This young lady is only one of many residents in Britain who decided to go to Syria to 'help' in a variety of ways, on many sides, not just ISIS. Who did what is hard to prove, particularly in a British court. Who's a threat to whom if they return is difficult to confirm.
This one may, after a decade or so to reflect, accept that she was misguided when she was persuaded to leave the UK at age 15. We're told her father had returned to Bangladesh and married a second wife before she'd left Britain. She might not think her husband was so wonderful helping to produce 3 children in a war zone. She might reflect that speaking without a lawyer present to various members of the media was bound to highlight her in ways to promote many causes, but not primarily hers.
By then she may have considerable reason to believe she had been neglected, used and abused. However, from where she is now it's doubtful if she can think very clearly about anything. She's one of many, the stories of the others as yet untold. The challenge is how they can be assimilated back into peaceful societies, globally. If we can't do that we'll end up with a significant proportion becoming more radicalised, and more dangerous. Not easy to to resolve, but at present I don't see this young lady as a major threat - unless we drive her to it. At present the attitudes of some might help do that.