The former Isis bride, 21, said she left east London with classmates Kadiza Sultana and Amira Abase because she was “young and naive” and wanted to help people in war-torn Syria.
Speaking on the documentary The Return: Life After Isis, Ms Begum told how the trio fell prey to Isis supporters online.
She revealed how recruiters played upon their guilt at seeing Muslims suffer in Syria and encouraged them to be a “part of something,” reports the MailOnline.
“I knew it was a big decision but I just felt compelled to do it quickly. I didn’t want to be the friend that was left behind,” Ms Begum said.
The former child bride is currently being held at the al-Roj camp in northern Syria after having her British citizenship revoked.
Top judges blocked her from returning to the UK after she was discovered in a Syrian refugee camp.
In the documentary, Ms Begum sobs while talking about the loss of her three children during the Syrian conflict.
She told of wanting to kill herself because of the grief and not having the strength to flee the bombings.
“The only thing keeping me alive was my baby I was pregnant with,” she said.
“I felt like it was my fault for not getting them out sooner even though I didn’t know why they died.”
Ms Begum gave birth to three children in Syria who all died during infancy.
Her third child, a son Jerrah, died in March 2019 just one month after birth.
Alba Sotorra, who directed the documentary, said Ms Begum was not a threat and needed help.
Speaking to The Times, she said: “In the beginning, Shamima was like a ghost just sitting there, covered, lifeless, like a marionette, a doll.”
The Spanish director was inside the detention camp making a film about a workshop run by a Kurdish woman.
“Her lack of ability to express her feelings made me feel deeply sad for her. Then, maybe two months after I met her, we had this game with the kids,” she added.
“The kids were playing with kites. Shamima was always very silent. And she sat on one of these carts watching. I saw a teardrop fall from her eye. It was the first time.”
In the documentary, Ms Begum begs the UK to give her a second chance because she was “still young” when she left.
“I would ask that they put aside everything they’ve heard about me and just have an open mind about why I left and who I am now as a person,” she adds.