Almost a condescending insult to assume Bangladesh would take her in. Which in reality they wouldnt. Thats like saying shes not good enough to come into UK but Bangladesh can take her. We are more valuable and see ourselves higher than the bengali people.
Funny enough their government has said in no uncertain terms she cannot go there. Also even if she was to apply for citizenship she'll probably be denied under the grounds of terrorism
You can either allow her back in Britain under arrestand sentenced to prison
Offer her deal in exchange for information, but she has to help rehabilitate others under close supervision on a 40 hour contract for the rest of her work life or something similar. Enforce it or send her to prison if she doesn't comply
Leave her in Syria to deal with the consequences. Which legally UK has to answer to a governing body on why she isnt allowed back in and left stateless.
On the flip side to fully understand this you need to go to the roots of how it all starts. What the causes are. Is it to do with what she watches on the news, sees on the internet, listening to radical teachers at the mosque. The mass destruction of muslim countries in the wars past?
On a larger political scale what are the government doing regarding foreign policy. When people are calling into LBC, CNN etc and echoing the same "mind our business" message everytime their are talks of new wars.
UK should be promoting a no more wars and meddling in foreign affairs message. A more inclusive culture for those already here. Inner cities should all be running anti radicalisation programs from primary school teaching positive british values. Not the pushing of agendas and left wing trickery. That might reduce radicalisation in the long run. It can still happen as UK historically has been directly involved in the destruction of Syria. Lebanon, Afghanistan and Iraq. A lot of that based on false intelligence and fake news.
Speaking of remorse, I doubt she'll ever be remorseful after seeing harrowing pictures from the previous wars in the last 19 years....So everyone can keep waiting on an apology.....