That she’s a UK citizen, whether we like it or not, and that should she return to the UK cannot be deported. (To where anyway? “The World Caliphate”?)
I agree with those who say 15 is an impressionable age, and that proper analysis of her current relationship with IS should probably wait until such time as she is somewhere she could reasonably be assumed to be speaking freely.
Having listened to her interview I think she sounds unremorseful, blasée about severed heads in bins, and having attitudes consistent with continuing to believe in the rectitude of IS principles, albeit that they have failed to live up to them. That said, I’m not a mind reader, and would agree that it is possible she’s being careful about what she says.
I can see no reason, on the face of it, for the diplomatic service or anyone else to bust a gut getting her home, unless for reasons of seeking a prosecution.
I would point out that the age of criminal responsibility in England is 10. The James Bulger killers, for example, were held responsible for their actions.
IS combatants aged younger than this 19-year-old woman are justifiably killed in battle. They are a vicious aggressor force, with an appalling human rights record. Using force against them is just, and supporting insurrection against their oppression is imperative on anyone who professes human solidarity. It is not necessary to ask what age they joined up when in the heat of battle.
She admits to travelling to Syria with the intention of joining the Caliphate and applying to marry an IS combatant. She seems to say she does not regret joining IS. This is appears to be admission of a crime in English law. She should therefore be investigated. It would seem to me there is a case to answer. If so, she should be tried for it. If the justice system deems it appropriate to seek her extradition, I could see the logic in that. I wouldn’t see that course as a priority, though.