I like the small CF stuff, like the Hornet, Bee, 25-20, 221 FB, etc. I assume she's not going to hunt the things, but rather take shots of opportunity. Therefore, long range fire-belchers are out, ad are the 223's & larger due to noise (I suspect there won't be any hearing protection used). The rimfires are OK for really short shots (50 yards or so) if placed well, but I'd avoid them as they tend to require a higher level of expertise.