That doesn’t help resolve if the previous Jemma was earlier or later in her timeline. What if something else happened and the wedding never happened. It would be just FitzSimmons luck if it did

Help. Jemma’s immediately grateful, the Doctor needs help, because Fitz should be in there somewhere.

“I hate to phrase it like this but are you ‘the Witch?’” She sounds embarrassed saying it, but that’s the only name the Doctor gave.