Given the options out there, I'd suggest handling a few.
I like the grip safety on the XD, just because I feel better about tossing it somewhere. For a purse gun that could get mixed up with other stuff, I'd consider something with more safety provisions than a Glock.
I know the Glock cult will attack this assertion, but my question is simple: how can it hurt to have a safety system that accounts for more possible types of accidents?
If it's not a purse gun, and it will be in a secure holster, then this is much less of a concern IMO.
Various pistols have different ergonomics. I'd try a few if she can. Some will feel natural, some will feel odd, some will feel downright wrong. Given the number of quality guns out there, I'd pick the one that feels natural in the hands.