As everyone else has pointed out, SHE has to feel comfortable with whatever she ends up carrying. My wife had the same problem. I have Glocks, but she doesn't like them or the caliber. We rented a few guns at ranges to see if we could find something she liked. After a CHL class had finished up, the instructor hung around for a bit. We started picking his brain, and he recommended an M&P9c. He said he even had some she could shoot. He showed her the interchangeable backstraps and away she went. Right off the bat she was very accurate with it, and the size was perfect. The search was over, so we bought one at the range THAT DAY. She still loves it and actually asks ME if I wanna tag along to the range with HER!!! I love it, and haven't said no yet!
![fire :fire](./images/smilies/fire.gif)
IMHO, start by grip. Find a weapon that feels right in her hand. A lot of manufacturers have gone to the interchangeable backstraps now, and this is at least partly due to the increase in sales to women. It just takes time to find "the one", and that's half the fun too, for both of you. Good luck!