Now, after giving birth to a baby boy, she says she has left the group and wants to go home.
Three years ago, British teenager Shamima Begum ran away from her London home with two other school girls and joined ISIS.
Now, after giving birth to a baby boy, she says she has left the group and wants to go home.
"One of my biggest priorities is my child. Because I left because of him. So I wouldn't want him to be taken away from me. Just try to give him a better life," Begum told Sky News Sunday.
Begum says the terrorist group's online recruitment videos were what initially attracted her to ISIS, along with a sense of security.
"It was like how they, you know, showed it in the videos, like, you come, you make a family together, and then afterwards things got harder, you know, when we lost Raqqa, we had to keep moving and moving and moving."
During the time she spent with the extremist group, Begum said she gave birth to a boy and a girl who both fell ill and died.
Now, the 19-year-old is living in a camp in northern Syria for those who have been displaced.
She said she has appealed to the government to help get her back to the U.K.
Now key questions remain — will she be allowed to return and can she readjust?
"It would be really hard. Everything I've been through, you know. I'm still ... I'm still kind of in the mentality of ... the whole planes over my head and having the emergency backpack and starving and all these things. It would be a really big shock to go back to the U.K., make a ... start a life again."
It's unclear how Begum is trying to get home.
According to The New York Times, it may be even more difficult than she anticipated.
British Home Secretary Sajid Javid said he wouldn't hesitate to block the return of those who left to support terrorist groups abroad. Britain's security minister warned that anyone who supported foreign terrorist groups would be investigated and possibly prosecuted.
If that happens in Begum’s case, her family has said they will care for her baby.
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