I went to Arizona State, which was (and probably still is) an absolute haven for bike thieves. Personally, I wouldn't send the Trek. I think it'll be snagged quickly and it's too nice a bike to lose. One thing I learned was that popular brands were stolen more often, so I'd look for a good quality off-brand. Here locally, for example, there's a surprisingly nice Shogun Selectra that's going dirt cheap. It wouldn't bother me to ugly it up, and I don't think Shoguns are going to be targeted by thieves like a nice Trek model would be.

Also, make sure she knows that you gotta lock both wheels AND the frame, and take the seat with you.