Not sure if it has been mentioned, but did she have her citizenship revoked?
If so, who gives a ****
If not, the UK is under a moral obligation to take her back, or at least make sure she isn't harmed.
Personally my opinion would be to take her back, but under the proviso it is to monitored detainment indefinitely (probably add a pretend trial to make it look nice). This will give them a lengthy period to see if she can be rehabilitated, keep her kid and evaluate whether she could/should be released to the public.
Again. Forgive me if I missed it as I only have time to skim, but from what I understand she didn't actually kill anyone, just got treat like a play toy for the nutty blokes with the bombs and guns.