Since your wife is the one who decided that she wants a knife for hiking, you probably needn't go too far down the "look, honey, isn't it precious" path of knife-buying (of course, that doesn't mean you should leap straight on towards the "Eviscerator 9000 Tactical Nightmare Knife" either).
That danged Chipmunk is really cute, though. And, I mean, it's called the "Chipmunk", for crying out loud.
How large are your wife's hands? I find that the mid-sized knives from Spyderco are very comfortable in my (admittedly puny) hands. The Native someone mentioned is a nice, ergonomic little utility knife and comes in CPM-440V. The Calypso Jr. Lightweight is a bit prettier, the micarta version prettier still. None of the knives mentioned are so pretty that you'd balk at taking them out into the woods and beating the crap out of them, though. All have pocket clips -- nice because you can still carry them if you don't have any pockets (just try clipping a Buck 110 to a necklace) -- and should be under 100 bucks.
Those are my suggestions -- the very best thing, though, would probably be to take her to a knife shop, have her pick out something she thinks is comfortable, and take it from there. Good luck!
