Chelsea felt like the black sheep of the family. She couldn't pass the academic criteria to go to Oxford like sister Libby, but she had more brains than people gave her credit for.
Though on the surface she was vain, indulged, and argumentative, this was a cover - she wasn't as tough as she made out.
Chelsea had several romances on the Square - Grant Mitchell, Sean Slater, Dr Al Jenkins and Jack Branning to name a few - but she never found true love. When her father Lucas came back into her life, Chelsea could have been forgiven for thinking that the normal life she craved was just round the corner.
However, Lucas was a murderer, accidentally killing his ex Trina and deliberately killing Denise's ex Owen - he then held Denise hostage and faked her death. When Denise escaped and Lucas was convicted, Chelsea struggled to live a normal life.
She decided to leave Walford for sunnier climes, where we hope she's found the peace and normality that she always dreamed of.
Upon Chelsea's arrival, she is seduced by Grant Mitchell, unaware he is dating her to make Jane Collins jealous. However, when Denise uncovers the truth, Grant ends the relationship. Chelsea finds employment at Tanya Branning's salon, Booty and falls for Sean Slater. Although, Sean is promiscuous and pursues other women, including Tanya and Carly Wicks, while Chelsea wants a serious relationship. Attempting to keep Sean away from Carly, Chelsea sets her up on a date with Warren Stamp, who tries to assault Carly. Sean rescues her and animosity between the girls escalates, particularly when Sean dumps Chelsea for Carly. Carly's brother, Dean Wicks, is attracted to Chelsea and, using this to her advantage, she and Deano sabotage Carly and Sean's relationship. When Patrick Trueman is attacked, Chelsea and Deano frame Sean, stealing CCTV evidence that clears Sean but Carly finds it and gives it to the police. Sean is released and the police charge Chelsea and Deano with perverting the course of justice. Sean gets revenge by cutting Chelsea's hair while she sleeps and having Deano beaten by a gang of thugs. She and Deano are sentenced to six months imprisonment and released after three.
Helped by her sister, Libby, Chelsea traces her father, Lucas Johnson, who left her and Denise 20 years ago. She confronts him, revealing that she is his daughter but leaves before he responds. Two months later, Lucas appears. Chelsea is reluctant to see him but eventually agrees to go out for a birthday meal. However, she leaves on discovering that she has a half-brother, Jordan Johnson.
She buys drugs from Sean and steals money from work to buy more but gets beaten up by a group of girls. Tanya fires her and Patrick catches her taking cocaine. He locks her in her room and calls Lucas to help. When he arrives, Chelsea has escaped through the bedroom window. Lucas finds her in R&R nightclub, high on cocaine, and takes her home. Chelsea gets her job back at Booty. She falls in love with Theo Kelly, but upon dating, Chelsea feels excluded from Theo and his university friends. She later cheats on him with a footballer named Ellis Prince, who offers her drugs. A guilt-ridden Chelsea confesses her infidelity to Theo and despite his forgiving her, insists she cannot be with him and ends the relationship. She resumes her relationship with Ellis but Lucas finds the drugs Ellis gave her and confronts Chelsea. She runs away with Ellis, leaving a note for her family but returns on Libby's birthday, demanding to know why Libby's grandmother, Liz Turner is in Albert Square, forcing her to admit she has been visiting her father, Owen Turner, in prison and is glad that he is going to be released. Chelsea is cautious of her family's safety when Owen returns to the Square, and pleads with him not to bring up the suspicious death of Lucas's ex-wife, Trina Johnson, again as Denise was a suspect and could get in trouble.
Chelsea and Roxy Mitchell both pursue Dr. Al Jenkins, becoming rivals as the doctor is dating them both secretly. Chelsea assists Jordan in his protest to get a tree planted in Trina's memory and manages to win Al. However, just before Chelsea and Al get together, Roxy turns up at his office dressed as a nurse, so Chelsea leaves, embarrassed. Despite this, when Roxy inherits The Queen Victoria public house, she employs Chelsea as a barmaid. Denise sets Chelsea up on a blind date with an associate of Lucas's called Matthew, but Chelsea does not enjoy the date and tells Jack Branning she wants to leave. While she is in the toilet, Jack tells Matthew that Chelsea has a boyfriend so he leaves. Chelsea and Jack start dating and she returns to work at the salon, now named Roxy's. When Jack is shot and hospitalised, Chelsea declares her love for him and stays with him in hospital but Jack ends it as he is still in love with Ronnie. Later, Chelsea and her colleague Amira Masood worry that they are pregnant and take pregnancy tests. Amira's is negative but Chelsea's is positive. She decides to keep the baby but decides not to tell Jack as it would not change anything but she does not want to be a single mother. After Denise sees Chelsea crying and spending time with Zainab Masood's baby, Kamil Masood, she tells Libby that she thinks Chelsea is pregnant. Chelsea admits it when Denise asks her and they have a heart-to-heart, which Lucas joins in. She takes the test again and realises she is not pregnant but tells her parents that she'll make her own decisions. She tells Amira that it was her test that was positive and promises to keep her secret when she leaves Walford after learning that her husband Syed Masood is gay.
Chelsea goes on to celebrate her birthday and discovers Denise has put a picture of Chelsea in the newspaper wearing a cowboy suit. Much to Chelsea's embarrassment, so she decides to buy all the newspapers so people will not mock her. When Roxy discovers it is Chelsea's birthday she decides to throw her a western themed birthday. Chelsea starts to fall for the DJ but Roxy is caught kissing him.
When Owen's body is discovered buried under the Square, Denise is taken for questioning. Chelsea thinks that Denise may have killed Trina and Owen as Lucas had told her that Denise was hiding Trina's bracelet in her bag. Chelsea tells Libby about the bracelet, and after Denise is released without charge, they see her leaving the Square alone and receive a text message from her saying "I'm sorry", unaware that Lucas killed Owen and confessed to Denise, took her to a canal and strangled her, sending the text message before he threw the phone in the canal. The police tell the family that Denise's car has been found by the canal and a body is pulled from the water along with Denise's mobile phone. Chelsea wonders who her mother really is and says it makes her some kind of monster. She offers to go with Lucas to identify the body but she is unable to go in so he goes in alone and identifies it as Denise, leaving Chelsea devastated. Chelsea believes that her mother killed Owen and then herself. After Denise's funeral, Chelsea and Libby agree to start packing up Denise's belongings. While celebrating Libby's birthday, Denise walks in, revealing that she is not dead but that Lucas has been keeping her prisoner, and that he killed Trina and Owen. Chelsea tells her to stay away from her, calling her a murderer. Lucas enters and confirms that Denise is telling the truth but Chelsea says he is covering up for her and she faked her own death. However, Lucas takes the family hostage, but when Jordan arrives, they escape and Lucas is arrested.
Chelsea says she no longer has a normal family, and argues with Libby over their parents. After speaking to Liz, Chelsea decides she wants to move to Spain with her, as people in Walford will only ever think of her as the daughter of a murderer. Denise initially argues with Chelsea about this, but eventually agrees, encouraging Libby to go too for a holiday before returning to university. After leaving drinks in The Queen Victoria pub, Chelsea, Libby and Liz leave Walford in the back of a taxi.
In November 2011, Amira states that Chelsea is living in Málaga, Spain. In May 2014, Denise goes to Spain with Libby to celebrate Chelsea's birthday. In August 2015, when Libby returns to Walford for her birthday, Chelsea calls her, urging her to tell Denise something, but Libby cannot go through with it. In December 2015, Libby reveals to Denise that Jordan briefly lived with her and Chelsea in Spain, however he caused an endless amount of trouble for them, so Chelsea kicked him out.