Shamima Begum has allegedly told her friends that she will never name other British people who joined ISIS.
Begum, 22, said earlier this week that she is not a threat and begged to come back to the UK, arguing she could help fight terrorism.
But a source told The Sun that naming British ISIS fighters from Syria is a “red line” for Begum, despite intelligence being “patchy” and potentially benefitting from her insights.
Begum was 15 when he left London to join ISIS, but said on Wednesday that her decision was a “mistake” but that she did not help the terrorist group.
She had her UK citizeship revoked by the Home Office and lost her Supreme Court bid to come back to Britain.
Begum, who gave birth to three babies who subsequently died, apologised to anyone affected by ISIS and said she too has suffered because of the group.
‘I was fed a lot of information on the internet’
She told Good Morning Britain: “I did not want to hurt anyone in Syria or anywhere else in the world.
“At the time I did not know it was a death cult, I thought it was an Islamic community I was joining.
“I was being fed a lot of information on the internet by people.”
In June, an ex-US diplomat who met Shamima Begum said she should be allowed to come back to the UK as she is “not dangerous”.
Peter Galbraith said he spoke to Begum in the Syrian camp where she has been living, according to The Telegraph.
She allegedly told Galbraith that she had stopped any form of contact with the terror group.
‘She’s not a dangerous person’
“I’ve talked to Shamima. She is part of the group of women who have absolutely rejected the Islamic State,” Galbraith said.
He added: “I know enough about her to feel quite confident that she’s not a dangerous person.”
“The basic position of the British government is that Shamima is somehow dangerous, and I just don’t think that’s true.”
Earlier this year, Begum said she was “just a dumb kid” and asked UK people: “Can I come home please, pretty please?”
And a court heard there is “overwhelming evidence” that Shamima Begum was a victim of trafficking when she left the UK.
Samantha Knights QC said that “the counter-terrorism unit had suspicions of coercion and control” at the time Begum left the UK, which she argued “gives rise to the need to investigate the issue of trafficking”.
In written submissions, Begum’s legal team said the Home Office failed to consider whether she was “a child trafficked to, and remaining in, Syria for the purposes of sexual exploitation and forced marriage”.
David Blundell QC, representing the Home Office, said at the time that it is “significant” the allegation is not that Begum was trafficked, but that “she may have been trafficked” – and that the teenager herself had not claimed that.
Related: Shamima Begum is ‘no danger’ to UK and should return, ex-diplomat says