Take her to the gun store and let her hold several different brands and types. Let her pick the one that best fits her hand. Then, take her to the range and let her shoot a few. If she's never shot a gun before, have her start with .22. It's a good caliber to get people started as it shows them the recoil, but not in a less-violent way than most everything else. After that, if she's willing, have her shoot a 9mm.
Some people may tell you that .22 is terrible for home/personal defense. But the fact remains that ANY gun is better than the one you DON'T have.