As Bodd above.
There are internationally recognised laws that state any individual cannot be "Made Stateless"
If the "Bride" has only one state in this case the UK and is not officially recognised as a passport holder, or a fully recognised citizen of A/N other country, then the UK must accept the "Bride" back into this country, no exceptions! this is international law.
One would assume that when, not if the "Bride" returns She will be segregated and interrogated as to what was the original motive for going in the first place? was She radicalised by internet from abroad, or was it radicalisation from within the UK?
As an aside?? how many Ex- DIASH fighters, not, camp followers have returned to the UK ?
What makes this case such a celebrity issue is the media froth and bubbles?
Ken