One thing to keep in mind is that a semi-auto uses the recoil in combination with the resistence provided by the hand/arms to cycle the round. It is possible to have a misfeed if the arms are not kept stiff enough during the recoil. This problem doesn't exist with a revolver.
Not sure it is much of an issue, but a potential consideration. Ultimately - it should be the firewarm that she is the most comfortable with. I'd recommend going to a range and having her try as many different types as possible.
Very good point . I have seen big strong men , whose limp wristed hold caused a malfunction .