She's a 19 year old, without ready access to weapons, in a country in which her ideology is both despised and very much visible. Sure, she's a pretty appalling human being, but the idea that she presents an existential threat to Syria is inflating her importance to match her own egotism. She's much more of risk to the UK, where there is a ready audience for her vile ideas and where she would get support from like-minded people and her family, than she is in Syria, where she's just a loser in a refugee camp.
That’s not really true, it assumes the power of foresight that ISIS were going to lose the whole time she was there.
She went at a time when ISIS was very powerful and controlled are large area spanning several countries. She actively promoted the ISIS power systems and infrastructure and in particular acted as a recruiting tool for male jihadis to join up and start a family there. ISIS’s whole caliphate was based on the idea that the faithful would flock there to support and defend the caliphate.
She probably has had access to weapons, we know women in ISIS have fought. Foreign women in ISIS were particularly active at oppressing, torturing and killing the local female population and acting as morality police. Given that she appears to have moved with the receding ISIS front, only leaving it when defeat was absolutely certain, also makes it very likely she was armed and fighting to some extent reasonably recently.
She might not be an ‘existential threat’ now, but foreign women joining ISIS really, really were a threat for a good few years.
Minimising that by saying she’s just a loser in a camp is just wrong. She was an active adherent of a philosophy which intentionally caused huge harm to others.