No Achievement for finishing Halo3?
 

Ok, so I completed Halo 3 a while ago and got all the achievements I should have. Just this last week my GF and I are decided to play it together on legendary. We beat it tonight and during the game she got each achievement on her profile for every level we beat. But then when we beat the game. I got my Heroic and Legendary completion achievements but she didn't get hers. Now... she's not even on XBOX live, but this means a BUNCH to her. I'm trying to figure out why she didn't get her achievements and what I can do about it. Any ideas? This is the first XBOX Live game she's played and the first set of achievements she's even cared about; she loves Halo.

Edit: I found out why... It reset her profile for some reason in Halo when we turned it on this time. It only shows that she has completed the last 2 levels and has locked out the rest of them until she starts from the beginning. Any way to fix this?

It's a bug, I don't think there's really any way to fix it other than going through it again.