I also agree with Yvaine. Especially since enough time has passed for Student to move away and move back.
That said, I do think you have to be somewhat more careful with how you publicly present your romantic rel
ationship if it began as a mentor/mentee rel
ationship. That doesn't mean you shouldn't have the rel
ationship, you just need to be more aware about it.
While I was typing, you updated with this:
Said student doesn't need Professor's reference anymore so that wouldn't be an issue, but is more concerned about other professors/people at the university and what their thoughts on the matter would be.
(At my old university, one of the professors married a student and everybody talked about it-the whole thing was quite the source of gossip.)
This is what I mean about being aware of the public face of their private rel
ationship. I have a friend who married a teacher whom she met while student teaching. They were very careful to be both discrete and open at the same time. That is they were incredibly professional at work and extra conscientious about PDA (even things like hand holding) even when they weren't at work. But at the same time, they didn't try to deny the rel
ationship or come up with excuses if they were spotted together.