Sonia does not know she is pregnant until she goes into labour and Mo Harris delivers the baby. After her daughter is born, Sonia is taken to hospital and tells her social worker Ameena Badawi, upon meeting her that she does not want her baby. She names her baby Chloe and Sonia decides she wants Chloe adopted. Sonia hands Chloe over to Ameena, who takes Chloe into foster care. Martin and his mother, Pauline Fowler, discover Martin is the father, Pauline wants custody of Chloe, which Sonia is against. Martin agrees that he wants Chloe for Pauline's sake, but admits to his brother, Mark Fowler, that he does not want to be a father and Chloe is adopted by Neil and Sue Miller. The Millers change Chloe's name to Rebecca. In 2002, Sonia, now suffering depression over the guilt of abandoning her daughter, kidnaps Rebecca and barricades herself inside her house. Neil and Sue, understandably upset about Sonia's actions, give Dot Branning fifteen minutes to persuade Sonia to give Rebecca back before they phone the police. Dot successfully persuades Sonia to give Rebecca back.
In 2005, Neil and Sue are killed in a car crash and Rebecca moves in with Sue's mother, Margaret Wilson. Sonia reads about the crash in the newspaper and she and Martin, who are now married, are concerned for their daughter and decide to track her down to make sure she is well. Posing as friends of the Millers, Margaret allows the Fowlers into their home and it is only when they admit who they really are that she tells them to leave. Pauline Fowler, Martin's mother, demands to be part of Rebecca's life, causing upset. Sonia is furious when she discovers Pauline and Martin have been seeing her daughter behind her back. Eventually Sonia gives into her urges and grows closer to Rebecca too. Margaret decides to make Sonia and Martin Rebecca's legal guardians in case anything happens to her, unaware that Sonia and Martin have separated due to Sonia's lesbian adultery. Sonia persuades Martin not to tell Margaret that they have split up, but when the truth comes out, Margaret is furious and refuses to give Sonia guardianship of Rebecca. When Margaret has a fall and dies, Rebecca is given to Martin and Pauline refuses Sonia access, causing many rows.
Sonia and Martin reunite in December 2006. On Christmas Day 2006, Pauline dies just before emigrating to America. Rebecca saw Sonia slap Pauline before her death and believes that Sonia killed Pauline. Sonia tries to hush Rebecca but the truth comes out and Sonia is arrested following a row with Martin. After absconding with Rebecca, Sonia is cleared of Pauline's murder when Joe Macer, Pauline's husband, admits to manslaughter. Sonia leaves Walford with Martin and Rebecca in February 2007.
Rebecca returned on 15 January 2014, now portrayed by Jasmine Armfield, when Carol Jackson tells Sonia about her breast cancer. Rebecca is seen in October 2014 when Sonia discovers that she has been missing school to practice her guitar for music school with Charlie Cotton. Having arranged for Rebecca to appear at the Queen Vic, Charlie calls Sonia. Rebecca performs a cover song of "You and I" by One Direction. In March 2015, Rebecca, tired of strife between her parents, enters a rebellious phase of her life. She adopts a goth fashion style and insists on being referred to by her former name, Chloe, before deciding to go by Bex. Bex rejects Sonia as she has been living away from them, and they become further estranged when Martin reveals Sonia is having a lesbian relationship with Tina Carter. Martin, realising the situation may be his own fault, decides to have Bex live with Sonia, reasoning that she needs to spend more time with her mother.
Martin starts a relationship with Stacey Branning and moves in with her and her daughter Lily Branning. Martin plans to propose to Stacey and Bex gives him her blessing but is glad when they decide not to marry. Stacey gives birth to a son, Arthur Fowler, although unbeknownst to Martin, Arthur is not his son. When Stacey is diagnosed with and sectioned due to postpartum psychosis, Bex realises Martin is struggling with Arthur, Lily and work, so she draws him up a schedule. She accompanies Martin on a visit to the hospital to see Stacey. When Martin learns the truth about Arthur's paternity, he goes to stay with his sister Michelle Fowler in America and when he returns, he intends to leave for good. Martin then reveals that Kush Kazemi is Arthur's father to everyone in the pub, including Bex. Martin tells Bex that Arthur is still her brother, and Bex later explains to Stacey that she hurt her father. When Martin and Stacey get engaged, Martin tells Bex, who says that Arthur really is her brother now.
Bex takes Louise Mitchell to school on her first day and when Louise has a fight, Jay Brown collects her and the girl she had a fight with turns out to be Jay's girlfriend, Linzi Bragg. Bex and Louise tell Jay that Linzi is Bex's friend, Star, and is 14. Linzi gets upset when Jay is adamant things are over, and Bex comforts her. Bex tells Linzi's mother, Thelma Bragg about the relationship, and points out Jay to her when she demands to know who has been having sex with Linzi. Although Jay has not had sex with Linzi, Bex states that Thelma's accusations are true. Jay is arrested and Bex is interviewed by police. After Bex tells Sonia that she has had sex, Sonia, Sharon Mitchell and Honey Mitchell, talk to her and Louise about the pressures and consequences of sex, but Bex reveals that she has not had sex. When Sonia finds a lump in her breast, she tells Bex, who fears that Sonia has cancer, but it turns out to be a cyst. Bex has a crush on newcomer Shakil Kazemi and is jealous when Louise flirts with him. At Martin and Stacey's reception, Bex and Shakil kiss, seen by a jealous Louise. Martin struggles to accept Bex dating, and after disputes between Martin and Shakil, Sonia gets them to make amends for Bex's sake.
Tina's mother, Sylvie, later moves in with Sonia and Tina, but Bex does not cope looking after her when Sonia and Tina are not around. Bex is stunned when Shakil tells her he wants to have sex with her. Bex tells him that she is not ready for sex and she talks about it with Louise, who tells her Shakil will not wait for long. After taking advice from Louise, Bex decides to change her appearance. Bex confides in Stacey about Shakil wanting to have sex, who mentions this to Martin; Martin interrupts Shakil's party, but later apologises to Bex.
Sonia is offered a job in Kettering and Martin and Stacey agree for Bex to live with them. Bex is angry and upset with Sonia and refuses to say goodbye, but Tina arranges for them to talk. Bex is upset and Shakil comforts her. Bex moves in with Martin and Stacey, but struggles to cope with the overcrowding until they move into Sonia's old house. When Bex discovers Shakil has bought condoms, she cancels her 16th birthday party to avoid him. Stacey advises Bex to tell Shakil how she feels. When the pair are alone in Bex's room, she stops him from going further than kissing, so he calls her frigid. However, Shakil apologises to Bex and she forgives him. Bex finds out from Louise and Shakil that people are talking about her relationship and about her and Shakil not having sex. Shakil suggests to Bex they send explicit photos of themselves to each other instead of sex. After talking with Louise and Tina, Bex decides to take an explicit photo. She tells Louise she has not sent the photo and thinks Shakil is not interested in her when he ignores her. Bex confronts Shakil about his ignoring her and Bex admits to Shakil that she did not want to break the law and feared the photos being shared, but apologises for hurting his feelings. Bex then tells Shakil she wants to have sex with him and they try to arrange a place and time that they can be alone. Bex goes round to Shakil's, whilst his mother Carmel Kazemi and brother Kush are out and they have sex. Immediately afterwards, Shakil sees Bex and Louise talking and assumes Bex is telling Louise about it, so he ignores Bex and refuses to tell her if they are still together. Bex asks Stacey how to know if you're having sex right and explains how Shakil is behaving towards her. Bex is upset when Shakil changes his online status to single. An upset Bex tells Stacey she has been dumped, who tells Martin and she is left embarrassed when Martin publicly has a go at Shakil. Martin's aunt and godmother, Kathy Beale tries to justify his actions, but Bex refuses to forgive Martin or Stacey until she watches Shakil kiss Louise as part of the Christmas play. Bex shows Louise a prospectus for a college after deciding she needs a fresh start but decides to stay at her school's 6th form to study A-Levels.
Keegan Baker insults Bex and she finds out Shakil was one of the boys who teased Louise with Keegan and warns him to stay away from her. When the school closes early, Bex, Louise, Shakil and Keegan take a bus home, but the driver suffers a heart attack and drives through the market and into the viaduct. The students are trapped but escape through the emergency exit. Bex is upset to learn Martin is trapped under the bus, but everyone works together to get him out. Bex stops Louise from truanting after being teased over a video posted online by Keegan of the bus crash and Louise gets Bex to promise that she will not resume her relationship with Shakil. Convinced that Shakil is encouraging Keegan, Louise gets Bex's phone and sends Shakil's naked photo to her friends Alexandra D'Costa and Madison Drake and Bex is left distressed when she finds out what Louise did and that the photo has been sent to another person. Bex remains angry with Louise, Madison and Alexandra for the way they have treated Shakil and is hurt when Shakil tells her she can "drop dead". On Valentine's Day, Bex receives a card and believes Shakil sent it, however, she realises Louise, Madison and Alexandra played a prank on her. Shakil tells Louise that he has seen Bex and Travis together and Madison and Alexandra tell Louise they believe Bex has been after Travis for a while, but when Louise confronts Bex, she insists they are just friends.
Bex takes a liking to Preston Cooper, a student from the United States, with whom her aunt Michelle had an illegal relationship. Preston encourages Bex to skip school and Preston gets Michelle to Sharon's house, where he is in bed with Bex, and Michelle realises Preston is using Bex to make her jealous. After finding out Bex had sex with Preston, Madison and Alexandra spread the fact, and Keegan and Shakil find out. Keegan suggests to Shakil they should get revenge on Bex, and Keegan imposes Bex's face on a porn video and spreads it around. Bex is humiliated when Martin sees the video. Bex and Martin meet with one of Bex's teachers, where Bex refuses to name anyone involved and they are told it is being passed onto the police as it is treated as an image of child abuse. Martin is called into school and is informed about Shakil's explicit photo. Bex takes the blame for sending it and she and Martin are told Bex will be interviewed under caution by the police the following day because she has distributed an indecent image of a child. Bex overhears Martin talking negatively about her to Stacey. When she tells Louise that she will admit the truth, Louise confesses that Madison and Alexandra were responsible for sending the photo and she should think about bringing them into it.
Bex is cautioned and tells Louise, Madison and Alexandra she took the blame despite being the only innocent person, and they laugh at her. The police and social services visit Bex, Martin and Stacey to ask about explicit photos Bex took of herself. Although Bex thought she had deleted the photos and had not sent them on, they had been backed up automatically. Bex is told she can return to school, but when Martin returns her phone, she only receives abuse so decides to do an apprenticeship, which Martin disagrees with her doing. Kush persuades Bex to return to school and not let what is happening ruin her life. Madison and Alexandra overhear Bex insult them when she confronts Louise over their friendship. In the toilets, Madison and Alexandra push Bex, tear her shirt and write on her face whilst Louise stands outside, worried about Bex but feeling unable to help. She admits to teachers Mrs Robyn Lund and Mr Gethyn Price that Louise, Madison and Alexandra were responsible for her attack and sending the photo, but Louise, Madison and Alexandra deny knowledge of either incidents and Bex ends her friendship with Louise, but Linzi offers her support. When Preston returns from Manchester, he and Bex become a couple. Louise finds out that Michelle and Preston are having an affair so tells Bex, who refuses to believe it until she sees Preston touching Michelle and Michelle flinching, so publicly demands to know if Michelle is having sex with her boyfriend. Preston apologises to Bex and admits he loves Michelle. Stacey and Whitney Carter stick up for Bex, ordering Preston to leave. While trying to find Preston, Michelle crashes a car into the chip shop after taking sleeping pills with alcohol. After this, Preston returns to America after being convinced that Michelle does not need him; Bex is glad that he has gone. Michelle tries to make amends with Bex, who reminds Michelle of what she has lost. Bex works alongside Michelle at the café and she snaps at Michelle when Madison and Alexandra make remarks about them and Preston.
Bex goes busking but almost backs out when she sees a group of girls laughing. Shakil persuades her to carry on, but she is stopped by Martin. When Alexandra sees Bex in the local shop, she knocks the sugar she is buying out of her hands and sticks chewing gum in her hair when she goes to pick it up. Later, Bex goes to the café where Kathy asks her to serve Alexandra and Madison their drinks. They insult her and Alexandra trips Bex, causing Kathy to spill soup on Madison. They later warn Bex that she can never escape them, and gain access to Bex's home by telling Stacey they are her friends and they smash her guitar. Bex is then tricked by them into putting mud covered in chocolate in her mouth, which the film and tell her it is cat faeces. Bex sees the video of this online and calls Sonia in tears, who returns to Walford and announces that she wants Bex to live with her. Sonia also visits Bex's school but does not mention Louise is part of the bullying when Bex asks her not to, which gives Louise hope that they can be friends again. After Michelle and Sharon get them talking, Louise agrees not to be friends with Alexandra and Madison, but in front of Bex she tells them she is not friends with Bex again, so Bex walks off in anger. Unknown to Louise, Madison and Alexandra plan to take revenge on her because they blame her for being reported to the school. Bex overhears Madison and Alexandra inviting Travis to a party at Louise's home, which Louise believes will just be for the three girls.
Bex tries to warn Louise that they cannot be trusted but Louise accuses her of being jealous because she has no friends of her own. Travis leaves Louise's party and tells Bex that Louise needs her. After Louise gets drunk and is sick, she staggers outside, coughs up blood and collapses, panicking Bex, Madison, Alexandra, Keegan, Travis and Dennis, who are watching. Louise is taken to hospital with paralysis and Sharon tells Louise about Bex finding her. When Louise is sent home, she invites Bex round, but Madison and Alexandra turn up so Bex does not go to Louise's house. After speaking to Dennis about the party on Travis's behalf, Bex tells Louise that Alexandra followed Travis into the kitchen and Alexandra interrupts them. Alexandra gets herself out of trouble by telling Louise and Bex that Travis may not have been responsible for spiking her drink and Louise insists that Madison and Alexandra are still her friends. Bex hears a rumour that Louise had sex with Keegan at the party, so she tells her to take a pregnancy test, but Martin catches Bex purchasing the test for Louise and wrongly assumes it is for herself. Bex is delighted when she learns Stacey and Martin are having a baby.
Sonia returns from Kettering and wants Bex to move in with her and her brother, Robbie Jackson and Dot, however, Bex wants to remain with Martin and Stacey. Alexandra decides she will take revenge on Bex when she overhears Bex smugly telling Travis that Alexandra will mess up in the showcase. Before Bex's performance at the showcase, Madison and Alexandra break a guitar string and when Bex looks for one in a classroom, Madison and Alexandra pin Bex up against a wall. Shakil hears the bullying through headphones and exposes it through the soundboard. Bex is found locked in the cupboard and she is encouraged to perform following her ordeal. Bex and Louise make amends and Bex decides to go the prom with Shakil. At the prom, Louise suffers burns after being pushed onto lit candles by Alexandra and Madison, leading to their arrests. Bex visits Louise in hospital but her mother, Lisa Fowler, says Louise wants no visitors and Lisa tells Bex her plans for Louise if she was well. Louise is distressed when Lisa and Bex arrange for Travis to visit her. Bex receives her GCSE results and is disappointed that she gained a D in music, so Sonia contacts Gethin about Bex's result and Gethin agrees to tutor Bex. Following a gas explosion, Bex tends to Gethin's wounds and they kiss.
Bex apologises but Gethin reassures her, however, he says he can no longer tutor her and says a relationship would be illegal due to the fact he is her teacher and insists he has no feelings for her. Bex attempts to make Gethin jealous by flirting with Shakil and Gethin asks her to stop her behaviour and he later kisses Sonia, watched by Bex. When Bex claims to have a new boyfriend, Gethin starts tutoring her again. Bex continues to pursue him but he insists nothing can happen, and Louise asks Bex not to chase Gethin. However, Bex tries to get Gethin to admit he likes her, but he goes through with telling Sonia that Bex kissed him. Sonia is furious that the kiss happened weeks ago and throws Gethin out. She asks Bex for the whole truth and Bex insists it was just a kiss and asks Sonia not to report Gethin. Gethin gets drunk and Bex's great-uncle, Jack Branning, Gethin's landlord, evicts Gethin when he finds out about the kiss. Gethin then leaves Walford. Louise accidentally tells Shakil about Bex and Gethin, and Bex is heartbroken when Shakil kisses Louise, though Louise is stunned and disgusted by Shakil's immaturity. Bex is devastated when Shakil is stabbed and killed in a knife attack in May 2018. The following year, overwhelmed by the prospect of going to Oxford, Bex takes drugs to cope with her exams and runs away; she is found by Stuart Highway. On the night of her leaving party, Bex writes a suicide note to her parents and attempts to overdose on pills. The following morning, Sonia finds her unresponsive in bed. She recovers well but decides to defer Oxford for a year.