The mother-of-three, who gave birth to her third child at the weekend, left east London with two friends in 2015 to join the terrorist group.
Metropolitan Police Commissioner Cressida Dick said counter-terror detectives will "deal with whatever they are confronted with" if 19-year-old Shamima returns to the UK.
"Because women and children are being killed back in the Islamic State right now and it's kind of retaliation".
Asked during the Sky interview if she felt she made a mistake going to Syria, Begum said: "In a way, yes. It concerns me. I suspect she was brainwashed", he is reported to have told the newspaper.
Even if this unpatriotic woman, who has expressed no remorse for joining a bloodthirsty gang responsible for the deaths of thousands, were to be prosecuted and imprisoned in the United Kingdom, she would not be inoculated against the virus of Isis extremism and Islamic fundamentalism. "Not just the fighting videos, but yeah the fighting videos as well, I guess".
Asked whether the United Kingdom should allow back Begum, who has given birth to a baby boy, Dyer replied: 'Yes, because I feel she needs a chance, maybe to explain what was going on and maybe we can understand a little bit more about how they got to her and how she felt it was the right move to jump on a plane and leave this country at 15 years of age.
"I don't want to take care of my child in this camp because I'm afraid he might even die in this camp", she said.
Begum was one of a group of schoolgirls from London's Bethnal Green neighbourhood who went to Syria to marry IS fighters in 2015 at a time when the group's online recruitment program lured many impressionable young people to its self-proclaimed caliphate.
She told the broadcaster: "I do feel that it's wrong that innocent people did get killed".
But to kill people like women and children, just like the women and children in Baghuz [Isis's last stronghold] who are being killed right now unjustly by the bombings - it's a two-way thing, really, because women and children are being killed back in Islamic State right now. I don't know how I would be seen as a danger.
While it is unclear whether Begum committed any crimes and her legal status is uncertain, it's possible Begum could face charges for supporting IS if she returns to Britain.
"Like, their justification was that it was retaliation so I thought "OK, that is a fair justification". Among the general public too there has been a chorus of calls for the lack of mercy shown to Isis victims to be extended to Begum and her newborn son. I know a lot of people, after they saw that me and my friends came, it actually encouraged them.
She added she had been "OK with" beheadings carried out by Islamic State adherents because she had heard it was allowed under Islamic law.
Lawyer Tasnime Akunjee told the Evening Standard he had "no idea" why she would make the remarks.