Just be gently persistant- even if it wasn't a bad crash, if it was on a bad day it could really rattle ones head and she may be avoiding the bike to avoid the Fear. I do that days out of every week. For some strange reason I'm still trying to dance with it, but taking a hit to the self confidence is tough. The tentativeness you mention sounds like the Fear, not change of interest. But I could be wrong, and she could need more time. You're in a better position to feel that out, I just think that once you've learned to fly it never lets you go. But I guess she needs to decide whether to fight that battle or let it go.
And you never know- your freind may come roaring out of the box next summer.

Lizzy