Shamima Begum has asked Britons to "give me a second chance", in a new documentary.
Begum was 15 when she and two other east London schoolgirls travelled to Syria to join the so-called Islamic State group (IS) in February 2015.
In The Return: Life After ISIS, a documentary by Spanish director Alba Sotorra that's premiering online at the South By Southwest festival in Texas, Begum is given therapy alongside other radicalised women from Western countries.
Watch: Shamima Begum should be allowed back to the UK, human rights lawyer says
The women are asked to write letters to themselves when they were younger about their regrets.
In the documentary, seen by AFP, Begum says: "I would say to the people in the UK, give me a second chance because I was still young when I left."
She adds: "I just want them to put aside everything they've heard about me in the media.”
Begum denies she "knew about" or "supported” IS's suspected rapes, tortures and beheadings.
She also rejects claims she could have been part of the terror group’s morality police, and said she was a "15-year-old with no Islamic knowledge" who didn’t "speak the language".
New pictures emerged this week showing Begum in Western clothes as she continued her fight to be allowed to return home to the UK.
Begum’s British citizenship was revoked on national security grounds shortly after she was found, nine months pregnant, in a Syrian refugee camp in February 2019.
She said she married Dutch convert Yago Riedijk 10 days after arriving in IS territory.
Begum told The Times in 2019 that her children, a one-year-old girl and a three-month-old boy, had both since died.
Her third child died in the al-Roj camp in March 2019, shortly after he was born.
In the film, Begum talks about feeling like an “outsider” in London and wanting “help the Syrians” before she left.
But she says as soon as she arrived there she realised IS was “trapping people” in order to make its numbers look more impressive during “propaganda videos”.
Director Sotorra said: "I will never be able to understand how a woman from the West can take this decision of leaving everything behind to join a group that is committing the atrocities that ISIS is committing.
"I do understand now how you can make a mistake."
The Return: Life After ISIS will premiere on Sky Documentaries and streaming service NOW this summer.
Watch: Shamima Begum silent after learning she can't return to the UK