I get exactly the same vibe off her as I do some of the girls at my school. Her truculence and inarticulate answers. Her “it’s not fair” and “but it’s not just me”. Even her “yeah I’m not even bothered”. It’s as though her emotional development has been arrested.
Upon initial viewing of the interview my impression was similar to yours, a kind of Islamist Vicky Pollard.
Having given this further thought and considered situations I have been in personally I am inclined to withhold judgement.
On several occasions I have been in the company of predators and criminals and feigned approval of their actions. On some occasions it has been to protect myself from physical harm and on other occasions it has been to encourage them to talk so that I could gain insight into their mindset.
I have no sympathy for even a teenage / minor person who who is attracted by atrocities to the extent that they travel to Syria to support an army of monsters.
However it is unrealistic to expect a teenager who is surrounded by said monsters and very aware of their love of beheadings, rapes and torture, to express disapproval of them until she is in such place as to be safe from retribution.
Her ex husband was (if my memory is correct) killed by daesh following suspicion that he was passing information to their enemies. It is easy to understand how she would wish to avoid the same fate, especially as deaths of alleged traitors to the cause tend to involve torture and prolonged suffering.
Possibly one of the strongest arguments for detaining her in the UK is to discover what she may feel inclined to disclose once she feels free to talk without fearing that she will have her head cut off / be burned alive etc.