Karen, Keanu and Bernadette arrive on Albert Square and Karen introduces herself to some of the neighbours, who are horrified by their rowdy behaviour. Louise Mitchell is horrified to discover that Keegan Baker, who claims to have had sex with Louise, is Karen's son and is moving in. Ted and Joyce Murray are also horrified to discover the Taylors are living above them, as Karen caused their friend to suffer a nervous breakdown when they were previously neighbours in Walford Towers. Karen is revealed to be on benefits. She is annoyed when the Murrays' friend, Joan Murfield visits, as Joan was Karen's former neighbours and regularly called the police about the Taylors. Denise Fox tries to make peace with Karen over her altercation with Keegan a few months previously, but Karen threatens violence against her if it happens again. When Louise tells her stepmother, Sharon Mitchell, that Keegan raped her, Sharon confronts Karen, so Karen punches Sharon in the face. Keegan, despite saying he made the rumour up because he likes Louise, is arrested on suspicion of rape and Karen is arrested for assault. Karen threatens Sharon with further violence. Keegan is not charged but Karen tells him she is ashamed that he lied. The family's dog, Bronson, ends up in the park's pond when he gets hold of Denise's handbag and Kush Kazemi pulls him off. Karen tries to get money out of Denise and Kush, but she backs down when Denise points out Bronson was off his lead.
Karen looks for work and after befriending Jane Beale, Jane convinces her husband Ian to employ her as a cleaner at their restaurant. Bernadette complains of being ill and Karen realises she could be pregnant so takes her to Dr. Natasha Black, who confirms she is pregnant. Karen asks Dr Black not to inform social services, and is against Bernadette keeping the baby. However, she later tells Bernadette is it her own choice, but Karen worries about how the family will afford to raise another child. Karen tells her sons about Bernadette's pregnancy when they argue that she is not really ill. Karen starts work for Ian but her constant talking annoys him and he sacks her after she takes burgers that she assumes are being thrown out. Karen pressures Keanu into talking to Bernadette about the father of her baby and then overhears Bernadette talking to Keanu, who Karen thinks may be the baby's father. Karen confronts Keanu, asking if he is the father, and Keanu is hurt that Karen thinks that, but admits the father is in Bernadette's year.
Karen and Bernadette clean the house for a social services visit and get some second-hand baby clothes. Bernadette steals some baby clothes from pregnant Stacey Fowler's and Karen scolds Bernadette's action. Karen ignores the bailiffs when they visit. Following a gas explosion, Bernadette suffers a miscarriage, devastating Bernadette, Karen and Keanu. Bernadette goes to see her daughter at the hospital and returns home with a box containing her daughter's footprints and is further angry with Karen for allowing the hospital to cremate her. Karen decides to do a memorial after speaking to Shirley Carter. Keegan punches Callum when he realises he is the father, but Callum joins the family for the memorial and Bernadette reveals they were going to name their daughter Belle. After Keegan's initial hostility, he admits to Karen that he blames himself for Bernadette's miscarriage as he was not there for her. When Riley and Chatham return home, they ask questions about the baby and Shirley comforts Karen when she breaks down.
After Keanu begins showing a romantic interest in Ingrid Solberg, Keanu agrees for Karen to meet her. When Ingrid is due to come round, Karen accidentally lets the bailiffs in. When Janet Mitchell is knocked over accidentally by Tina Carter, Janet's father Billy Mitchell wants to get Janet a dog. Karen agrees that Billy can have Bronson for a few nights for Janet. Karen panics when Riley and Chatham have been collected from school by a loan shark called Lloyd that she has borrowed money from. He allows her time to get the cash within 24 hours and she manages to get money by selling Riley and Chatham's games console. However Lloyd claims she is still overdue from the first repayment; he orders bailiffs to remove her television set which upsets Karen. Desperate for the cash, Karen reluctantly decides to pawn a wedding ring that she has kept. However Keanu tries to convince her not to as it had belonged to his grandmother. When Karen decorates the flat for Christmas, she finds Stacey's phone that was taken and hidden by Riley and Chatham. Karen finds out that it was Riley and Chatham when she confronts her children and Karen later takes on the role of the angel in the Nativity. When the Taylors belongings are removed by bailiffs due to Karen failing to repay loans and they can get them back the next day if they can raise £1000, Karen and Bernadette go to visit Karen's sister, Kandice Taylor. Kandice agrees to loan them the money, but when Karen begins arguing with her, Kandice changes her mind. Bernadette meets up with Kandice and emotionally pleads with Kandice to help, but she apologetically refuses to and when the bailiffs are due to visit, Kandice turns up with the money. After bickering again and Karen throwing the money back, Karen and Kandice make up.
When Karen sees Apostolos Papadopolous in the launderette, she accuses him of being an asylum seeker, without realising he is the owner, and he ejects her when she asks for a job interview. However, she calls him and puts on a posh accent to secure an interview. When she attends it, he is angry but she manages to convince him that she is the right person for the job and he offers it to her. However, she is confused when she takes down the job advert and it reappears. She is furious when she learns Masood Ahmed has been offered the job, so Apostolos says he will offer the job to whoever does the cleaning of the launderette the best, however, they argue and spill bleach, but later Masood says he was to blame so Apostolos offers Karen the job but only because an employment agency failed to send anyone. Karen then offers a personal ironing service to the customers in a bid to make more cash, but receives complaints when she mixes up people's clothes. Karen's ex-boyfriend and the father of Keegan and Chantelle, Mitch Baker, arrives on Albert Square and he is warned away from the family by Keanu, but he later returns and he shouts for Karen and Keegan at the flat, but Keanu punches him. Mitch flirts with Karen at the launderette whilst she is working and when Karen brings Mitch home, Keegan, Keanu and Bernadette do not want Mitch's presence, but Karen later sneaks him into the flat. Keanu is disgusted with Karen for letting Mitch stay the night and Mitch brings up Keanu's father. Karen attempts to reluctantly talk to Keanu about his father, but she fails and talks to Mitch about her being stabbed by Keanu's father. Karen considers re-conciliating with Mitch, however she discovers that he has a girlfriend and that his girlfriend is pregnant. Karen breaks up with Mitch and he leaves Walford.
Karen helps to contribute money to raise for Kat Moon's funeral and Karen is angry to discover that Kat is alive and her grandmother Mo Harris was behind Kat's "death". Karen tries to attack Mo, but Kat confronts her, causing a fight between the pair, which then leads to a bar fight. Karen and Kat continue their feud and when Kat advertises her cleaning business in the laundrette, another fight between the pair occur. However, both Karen and Kat make up and become friends. Karen is devastated to discover that Keegan has been stabbed. Keegan survives the attack but his friend Shakil Kazemi dies from his injuries. This causes Karen to remember when Keanu's dad tried to attack her with a knife whilst she was pregnant. Karen supports Keegan, who plans revenge against the boys behind the attack. Without Karen's knowledge, Keegan confronts some of the boys behind the attack and accidentally stabs one of them. Carmel Kazemi discovers the boy and lies to Keegan that he has killed him. Keegan discovers Carmel's lie and this leads to a confrontation between Karen and Carmel, but Karen understands Carmel's reasons behind the lie and forces Keegan to apologize to Carmel. Karen discovers that her son Keanu is having an affair with her married rival Sharon. She forces them to end the affair, but she learns that Keanu and Sharon are still sleeping together so she confronts Sharon. Keanu reveals to Karen that someone is blackmailing them and they discover that it is Louise Mitchell and Karen threatens Louise.
Mitch returns to Walford with his daughter Bailey Baker and he lies to Karen that Bailey is his friend's daughter. Karen later discovers that Bailey is his own biological daughter. Mitch wants Bailey to live with the Taylors as her mother Dinah Wilson is due to die from multiple sclerosis. Karen cannot let Bailey live with her because she has no space, but agrees to help Bailey and her mother. However, she agrees to let Bailey live with her when her mother dies. Louise's father Phil Mitchell sends Keanu to Spain to help him look after his business, but Karen is worried that she has not spoken to Keanu for several weeks and blackmails Sharon to tell Phil to bring Keanu back to Walford; otherwise she will expose their affair. Karen sees a photo of Keanu being beaten up in Spain and Phil goes back to Spain to bring him back. Meanwhile, Keegan's drug addiction is exposed when he almost overdoses and Karen has a fight with Whitney Dean, about her sister Tiffany supplying Keegan with drugs. Karen calls the police on Tiffany who is arrested and questioned. However, Karen agrees to drop the charges when she discovers that Mitch knew about Keegan's drug addiction and that it has been going on for a while.