Pachabal's Cannon was written by Pachabal, not Bach. Not to be a jerk, I just couldn't hold that in. Its a good one but also can be overdone...

It depends on how 'traditional' she wants to be. There are a lot of little ballad-y things that could work that are outside the norm. There are also lots of things that you could do with just a piano or string quartet arrangement of it. Choral songs for example - check out Dirait-on by Morten Lauridson. VERY pretty and holds up without the words. Dunno how it would work, but there's a chance.