Just to update, I spoke to the Passport Office and the person I spoke to wasn't sure - but
thought it would be OK (it could come down to the discretion on whoever deals with it
).
She has her citizenship ceremony on Monday, so we will find out. I'm guessing one of 3 things will happen.
1. The passport will be issued in her married name - all good
2. They will want support documentation to show the name change (if they can't already see the marriage certificate via JCAP)
3. They will reject the application - in which case she reapplies with her marriage certificate attached (which would be a pain but not the end of the world)
We will see. Unless anyone chimes in with their experience, I'll update again with the outcome in case anyone else find themselves in a similar position.