I understand your mindset, that said just getting her a pistol is not enough. She needs to be trained in its use and employment, and if she is not that into it don't expect much. If its just for home defense a light weight AR is a better choice for her.
Shooting is a perishable skill, and one that needs to be maintained to be employed effectively when your brain shuts down. Cause when it shuts down, and it will the training is what will take over. Case in point I took a county sheriff to the rage 2 weeks ago, he carry's a gun every day and served in the army and he could not shoot a simple 7 round dot drill at 7 yards to save his life. It took us 600 rounds to get him back to the point he was at before work, and married life got the better of him.
I suggest taking a class they are not cheep but they are worth it.
I know I talk to much but the point I'm trying to make is it may be more dangerous for her to have a pistol than to not with, out formal training and the mindset.
Not knowing your wife's build, history and mindset its very hard to make a good recommendation. My wife is 5'6" and athletic, she carry's a glock 19. It fits her hand very well and she shoots it very well, now that I have convinced her to drift the sights. If your wife is smaller than my wife she may like the glock 26 or a S&W revolver. There are lots of options out there, see what she likes. Regardless of the weapon chosen I would shoot a minimum of 500 rounds through it before I trusted my life to it. On new guns this is key as most need a break in, it will also identify any issue on a used gun.
On another note, gun store sales men for the most part are not the best people to ask in my experience they are more dangerous wounded bear. A 9mm is all she needs, with today's bullets your not giving up anything to a 45acp. Especially for a smaller framed inexperienced shooter.