Best advice I can give is to take your beloved to a gun range that rents guns and try out some until she finds one that she can shoot and hit with no problem... Best of luck to you !!
This. Also, a collection of friends with sizable gun collections along for the ride.
Myself and a couple of friends recently did this with a 30-something couple that had grown up in Chicago. Between myself and a couple of others, about 30 handguns were represented. .22LR, .380, 9x18, 9x19, .40S&W, .45 ACP, .38SP and .357. SA, TDA, DAO; striker and hammer fired. After a couple hour safety briefing at my house, off to the range.
Surprise? She liked the .40 XD best. He liked the 226. They ended up buying a 229 in 9mm for him/her and are still evaluating further while investing in some training.
Buying a gun for a novice shooter without getting some experience is like buying a first car without ever driving
anything.
Newsflash: No one WANTS to be shot by anything. True. It is a laughably moot point where a defensive firearm discussion is concerned though. Letting someone's lack of desire to be shot by a BB gun should have no bearing on a discussion about buying a defensive firearm. A deployable, controllable gun with reasonable accuracy and excellent reliability is the best you can hope for with a central-nervous-system-interrupting solution from a handgun. Handguns just aren't that effective under the best of circumstances. They're dang-sure no Willy-Wonka-Golden-Ticket to ending a bad situation.
Start with the largest capacity, largest caliber handgun you can.
Can she grip it effectively and perform the manual of arms? If not, go back to the top and start over.
Can she make rapid, combat-accurate followup shots? If not, go back to the top and start over.
If a carry gun, can effectively carry and deploy it? WILL she carry it or neglect to based on size? If not, go back to the top and start over.
Is it reliable? If not, go back to the top and start over.
Yeah, high capacity is always better. More mass penetrating a target with the necessary velocity is better. She MUST be able to effectively manipulate it, shoot it reasonably well and be a platform she will adapt to carrying.
Is a .22 mag revolver effective? It may be the most effective solution for her after evaluation but I sure wouldn't start with that choice without working my way "down" to it.