I'm not sure what you're doing to bash your knee so much when ice climbing. I've suffered lots of bashed knuckles, a bloody nose from a falling ice shard but, as someone having had one of my knees rebuilt twice, I don't recall any knee bashing, or at least nothing big enough for me to remember afterward.
If it's that big of a concern, maybe a neoprene sleeve might help. Have her wear snowboarding pants maybe (since some have padded knees)? Personally, depending on where you climb, it sounds like the approaches might be a bigger issue with her knee. Advil/naproxen and some good conditioning to strengthen the joint will help lots there.