I might be a bit late in my response...but I try anyway...and I hope I have understand you right
You say:
She is not that attractive physically!
Well in my opinion this is what you shall look for last.
But if a person gives you feelings like: "my old has crush reappeared for her again" and this feelings aren't blinded by beauty then your mind is trying to tell you something. Maybe your crush is because you feel a connection and like the way she behave.
This is the relationship you shall go for. Beauty will never keep you happy (it's a nice add on) feelings will
So maybe you will, when you look back at mine age, see a 40 years happy marriage withe mutal understanding.
Good luck:)