I watched the documentary re Shamima Begum and didn't find her a particularly easy person to warm to. However, I think she should not be stripped of her British citizenship.
She was 15 years old, seemed to have had a rather difficult family background, and was therefore vulnerable to grooming and promises of a happy ever after land. Also, there was a Canadian involved who seemingly encouraged and assisted her and the other girls.
Over the last eight years the girls she went out with have been killed, she has herself lost more than one child and has had no family to turn to while in a refugee camp. So in many respects her life over the last five years has been a sort of imprisonment.
Doesn't this judgment mean that a British citizen born of parents who were not from the UK is not being treated in the same way as a British citizen whose parents were from the UK? That seems like second class citizenship to me - and I think that is a sure way to create more feelings of alienation.
There must be several actual terrorists in UK prisons now who have planned or even committed acts of terrorism, but they have not been stripped of their citizenship. Presumably, when they eventually leave prison, if they are British citizens they will not have that citizenship removed.