Jamie is right. You both have to think this through very carefully. If she wants to or has to carry pistol, she has to be absolutely willing and able to kill her enemy without blinking or hesitating. And then, she has to be ready for the consequences of that decision, including taking another life and how that is going to affect her, and legal liability. She should know that pistol or revolver so well if she does have to use it, she wont fumble; forget how the safety works, all that. I’d say she should put hundreds if not thousands of rounds through it. She should be an excellent shot with it at defensive ranges, and be trained to hit center mass. Those that say head shot only or shoot to wound or firing warning shots make me cold, and they probably should get some training themselves. Those that carry a pistol or revolver to use to scare a potential threat should not be carrying at all, and are idiots of the highest order.
You also may want to consider other kinds of skills like the ability to carry concealed, what happens if a bad guy tries to disarm her, etc. Probably knowing her local gun laws and the consequences should be mandatory too before she actually carries. Where can you legally carry, when do you have to lock up the gun before you go in (federal property, courts, airports, private businesses that post no firearms, etc.). Also, not just shooting to kill, but awareness of those around her and the possibility of hitting an innocent person, shooting through a house or apartment wall and what that may lead to, etc.
The handgun should be small enough to conceal, but large enough she can actually hit her target without flinching before each shot, etc. Folks get so into mag capacity they forget that an average defensive shooting situation is not a gun battle, but putting down the aggressor and nothing more.
And, of course, there is civil liability to consider, as well. She may be in the right, may be defending her life, and still be ruined financially in the aftermath.
On more practical matters, consider what kind of concealed holster is best for her, and those can be very expensive, but cutting corners there can be very dangerous for her or even get her killed. And besides all that, have you considered revolvers? The single best thing about a revolver is no worries about the safety. She pulls the piece, sights and acquires her target and pulls the trigger. Fast reloading and high capacity should be the last thing for her to worry about.
Dane