Becca Swanson made her first appearance on 7 December 2009. She is portrayed by Simone James.
Becca is a friend of Stacey Slater's who Stacey meets when she is staying in a psychiatric hospital. When Stacey's mother Jean visits Stacey in hospital on 7 December 2009, Stacey is more interested in Becca. When Jean asks Stacey to come home for one day, Becca tries to convince her not to go. The next day, Stacey's boyfriend Bradley Branning and Jean come to collect Stacey, and Becca and Stacey say an emotional goodbye. Stacey visits her on 19 January 2010 and Becca reveals she is coming out of hospital soon but will be living near Brent Cross meaning it will be difficult for Stacey and Becca to see each other, as they want to stay in touch. Stacey later texts her, inviting her to stay in Albert Square.
When she arrives, she wants to meet everyone that Stacey has told her about, including Max Branning, Bradley's father who Stacey once had an affair with when she was previously married to Bradley. Later, Becca wants to take Stacey out but Bradley does not think she should be going out as she is pregnant. Becca asks Bradley if she is welcome there but he does not answer. In the pub, Becca tells Stacey the doctors thought it was too soon for her to come out and wonders if she should go back. She asks Stacey to call her a taxi. The next day, Stacey will not eat anything, so Bradley brings Becca back to stay and Stacey cheers up. Bradley allows Becca to sleep upstairs in his bed as she is paranoid about Archie Mitchell's murderer living on the Square. Becca tells Bradley that Stacey has told her about Archie, but Stacey assures Bradley that Becca does not know that Archie raped Stacey and that Bradley punched him on Christmas Day. Later, Stacey tells Becca not to say anything about Christmas or Stacey's baby. However, when Stacey auditions for a barmaid job, she goes to drink a cocktail and Becca reveals to everyone that Stacey is pregnant. The next day, Becca and Stacey look for jobs. Becca suggests opening a stall on the market, but Stacey says the market inspector, Mr. Lister, hates her. They ask Mr. Lister for a chance but he says no. Becca comes up with a plan, steals a suit from the laundrette and dresses up as a businesswoman. She puts on a posh accent and pretends to be from Walford Council, telling Mr. Lister that Stacey has lodged a complaint against him and making legal threats, using the name Amanda Swanson. Becca returns the suit and as Stacey and Becca work on their new stall, Mr. Lister tells Becca that her "sister" can stuff her human rights.
Becca starts to think that Stacey does not want her around and thinks that Bradley and Stacey are planning something, but Stacey insists it is not about her. She steals Ronnie Mitchell's hairbrush from The Queen Victoria and tells Stacey that she can take a DNA test to prove the baby is Archie's. Becca is upset when she is not invited to Bradley and Stacey's wedding and thinks that Bradley hates her. Bradley makes things worse when, after Becca says that he cannot take her best friend away from her, he tells Becca that they are planning to move. Becca tries to sneak the hairbrush back into Ronnie's room but Ronnie catches her and Becca tells her that Archie raped Stacey, leading to Stacey's discovery that Archie was infertile. Becca then calls the police about Bradley. Bradley and Stacey flee, but police chase him to a rooftop. Becca watches as Bradley falls from the roof of The Queen Victoria to his death. After visiting him in the chapel of rest, Stacey runs away and Becca and Jean try all they can to find her. Becca gets an address from Max of a flat they used during their affair, but after failing to find her, she decides to places an advertisement for Bradley's funeral service in the Walford Gazette in the hope that Stacey will see it and come to the funeral. On the day of the funeral, Jean prepares a dress for Stacey, but Becca wears it, which leaves Jean furious, and she says Stacey and Bradley were happy until Becca arrived. Stacey fails to turn up at the funeral. Becca comforts Max after the funeral, he is unable to resist her attempt to seduce him, so they kiss.
The next day Max tells her it was a mistake but she attempts to seduce him by stealing his daughter Abi's keys and laying naked on his kitchen table covered in cream and fruit. He tells her to get dressed and get out. However, after Max and the Slaters visit the body of a girl found in a river believed to be Stacey, Becca and Max have sex. Becca gets a phone call and leaves in a hurry, so a suspicious Max follows her to a flat where Stacey is staying. Max convinces Stacey to return home, and she and Becca decide to bring up the baby together after she tells Becca that Archie is not the father.
Refusing to allow Stacey to work on the stall due to her pregnancy, Becca comes up with a plan to make more profit. She asks Mo Harris to buy Whitney Dean's stock of T-shirts that Fatboy has promised to sell for her, then sells them on her own stall. She then tells Fatboy she had no idea the T-shirts came from Whitney and flirts with him. They eat chips together and when Fatboy says he has ideas for T-shirt designs for Whitney's stall, Becca asks to see them. He gives her a design so she has several T-shirts printed up, but fails to sell them and is humiliated when she realises that the design reads "chav" in the mirror.
Following the birth of Stacey's child, Lily, Becca grows increasingly paranoid of people trying to interfere with Stacey's life, leading her to accost Ryan Malloy when he shows up at the Slater house with a bouquet for Stacey. Becca is further devastated when Stacey throws her out of her room, as she thinks it is too crowded for Stacey, Lily and Becca at the same time. Becca starts to manipulate Stacey by deleting a message from Max about the scattering of Bradley's ashes, and then telling her that having his ashes is spooky, causing her to not want to go. She convinces Stacey to stop taking her medication and lies about Jean in order to cause a rift between mother and daughter. When Jean confronts Becca, she says if it was not for her, Stacey would be with a murderer, revealing that she was the person who called the police about Bradley. She tells Jean that if Stacey finds out, it will make her condition worse. Jean tells Stacey and Becca denies it, but Stacey says Jean has never lied to her, so Becca admits the truth saying Bradley was a killer. Stacey hits Becca so she picks up the urn containing Bradley's ashes and throws it at the wall. Becca then leaves after Jean tells her to do so.