On 28 January 2020, it was announced that Armfield had decided to leave the soap; she departed on-screen in the episode broadcast on 6 March 2020.

[2][3] Her storylines on EastEnders included being put up for adoption after her birth and returning to her biological parents after the death of her adoptive parents, being caught up in a custody battle between her parents and her paternal grandmother Pauline Fowler (Wendy Richard), her relationship with Shakil Kazemi (Shaheen Jafargholi), forming a friendship with Louise Mitchell (Tilly Keeper), being bullied by Louise and her friends, dealing with the grief of Shakil being murdered, discovering that her love interest Preston Cooper (Martin Anzor) has been sleeping with her aunt Michelle Fowler (Jenna Russell), becoming infatuated with Sonia's boyfriend Gethin Pryce (Cerith Flinn), getting into the University of Oxford, developing an addiction to ADHD drugs, dealing with depression and running away, attempting suicide, and overdosing during a boat party on the River Thames.

Bex, (now played by Jasmine Armfield), returned along with her mother Sonia (Natalie Cassidy) for a storyline involving Carol Jackson (Lindsay Coulson) being diagnosed with breast cancer.

"[7] When Armfield auditioned for EastEnders, she was unaware of the character she would be playing and was "surprised" when she found out, saying of her casting, "My agent called and I couldn't believe it...it was amazing news"..[8] With the introduction of Shaheen Jafargholi as Shakil Kazemi, Tilly Keeper said, "there will probably be maybe a little bit of a love triangle and a lot of jealousy" between Louise and Bex.

[10] David Brown, from Radio Times, says the storyline "tackles a topic that should be of massive concern to both tech-savvy teenagers and parents who fear they're being left behind when it comes to the way their offspring communicate" and "that the fallout of these rash actions" could lead to legal consequences for Louise, Bex and Shakil.

[11] Bex enters a storyline where she is bullied by Madison Drake (Seraphina Beh) and Alexandra D'Costa (Sydney Craven).

On one occasion, they are in a scene where Bex is brutally attacked in a school bathroom by the girls, and viewers were noted to be angry.

[19][20] After recovering from her addiction, she is then met with struggling to cope after being accepted by Oxford university and being rejected by former boyfriend Shakil's older brother Kush Kazemi (Davood Ghadami).

[20] After managing to pull herself from the crowds of the Queen Vic, Lisa Fowler (Lucy Benjamin) notices the brave face being put on by Bex and encourages Bex to tell Sonia about how she is feeling as Lisa sees past her brave face and also has a history of poor mental health.

After her daughter is born, Sonia is taken to hospital and tells her social worker Ameena Badawi (Shobna Gulati) upon meeting her that she does not want her baby.

In 2002, Sonia, now suffering depression over the guilt of abandoning her daughter, kidnaps Rebecca and barricades herself inside her house.

When Margaret has a fall and dies, Rebecca is given to Martin and Pauline refuses Sonia access, causing many rows.

Rebecca returned on 15 January 2014,[5][23] now portrayed by Armfield,[24] when Carol Jackson (Lindsey Coulson) tells Sonia about her breast cancer diagnosis.

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 (Lacey Turner) and moves in with her and her daughter Lily (Aine Garvey).

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.

When Martin learns the truth about Arthur's paternity, he goes to stay with his sister Michelle Fowler (Susan Tully) in America and when he returns, he intends to leave for good.

Martin then reveals that Kush Kazemi (Davood Ghadami) is Arthur's father to everyone in the pub, including Bex.

Bex goes round to Shakil's whilst his mother Carmel Kazemi (Bonnie Langford) and brother Kush are out and they have sex.

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.

Convinced that Shakil is encouraging Keegan, Louise gets Bex's phone and sends Shakil's naked photo to her friends Alexandra D'Costa (Sydney Craven) and Madison Drake (Seraphina Beh) and Bex is left distressed when she finds out what Louise did and that the photo has been sent to another person.

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.

Bex takes a liking to Preston Cooper (Martin Anzor), a student from the United States with whom her aunt Michelle (now played by Jenna Russell) had an illegal relationship.

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.

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.

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.

At the prom, Louise suffers burns after being pushed onto lit candles by Alexandra and Madison, leading to their arrests.

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.

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 (Ricky Champ).

She recovers well but decides to defer Oxford for a year, and once her life is back on track, she makes the decision to go travelling, which Sonia is unhappy about.