How does she feel about electronica? There are some out there that are nice and hard, and some that use more "real" instruments, if that matters to her. I'm actually quite a fan of the Tron: Legacy soundtrack that Daft Punk did (which is heavy on acoustic instruments along with electronics, and many of the tracks are conveniently short so wouldn't require much cutting). And the good thing about electronica is that there are often so many remixes to choose from so if you sort of like a song but not that much, you can see what ten other people did with it (also that it tends to be repetitive so cuts aren't a bit deal).
As others have said, look into songs with great instrumental interludes, like rocking guitar solos. (sorry, this list is going to be oldies-oriented 'cause that's largely where my flag flies)
--Hotel California (Eagles)
--25 or 6 to 4 (Chicago)
--Free Bird (Lynyrd Skynyrd)
--November Rain (GnR)
--Let It Be (Beatles)
Wow, I am drawing a blank tonight at accessing my mental list of "songs with great guitar solos." Sorry about that.
Also, look into live versions as those will often have extended solos, if you can find a version without a lot of crowd screaming and such.