The pregnant teen said she didn't regret joining the group and wasn't troubled the first time she saw the severed head of one of its execution victims - comments that will likely make it more hard for her to convince British authorities she is ready to rejoin civilian society.
But speaking to reporters, the now 19-year-old Shamima said that she had never seen an execution during her time with Isis, "but I saw a beheaded head in the bin".
"I feel like she doesn't understand there are other ways of thinking and a form of justice - she's so young that she hasn't done the research, the psychology of human beings and why people do the things they do. I'll do anything required just to be able to come home and live quietly with my child". "It's not really possible".
"Because I don't want it to be taken away from me, or at least if it is, to be given to my family".
Metropolitan Police Commissioner Cressida Dick said the teenager would be spoken to by counter-terror officers if she were to return to the United Kingdom from Syria.
She said she took him to a hospital but there were no drugs and not enough staff.
The chief of the intelligence service MI6, Alex Younger, said that he was concerned about jihadists returning to Europe with "skills and connections that make them potentially very dangerous".
"We as a society must learn that we can stop this from happening in the first place by trusting our Prevent strategy, reporting our concerns early and stopping people being radicalised, investigated and, most likely, criminalised by the poisonous rhetoric spewed by terrorist organisations of any ideology". "So they'd only have proof I didn't do anything that is risky", she said.
While she was aware of beheadings and executions being carried out by the extremists she said she was "okay with it", because she had heard "Islamically that is allowed".
She gave birth to a boy over the weekend, having already lost two children, and made pleas for forgiveness and to be accepted back in the UK.
It asked Begum's mother to ensure the decision was brought to her daughter's attention "along with her right of appeal to the Special Immigration Appeals Commission".
A combination of stills taken from CCTV on February 23, 2015, issued by the Metropolitan Police.
What can Shamima Begum do now?
In a letter sent to her family in east London, officials said the Home Secretary, Sajid Javid, had made the decision in "light of the circumstances".
Governments fear the return of foreign fighters could pose a security risk.
Mr Javid has been vocal in his opposition to Ms Begum's return but legal experts have argued that because individuals can not be left stateless he does not have the power to stop her unless she is a dual national.
Authorities have drawn a distinction between people who have actually fought under the banner of ISIS and those who joined the terror group as supporters.
"In order to protect this country, he has the power to deprive someone of their British citizenship where it would not render them stateless".
The petition created by Stephen Kent calls on the Government to ban those who have been part of terrorist groups.
"I did have a good time there".
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