S&W Bodyguard, S&W M&P Shield, and the new Sig P365 are all worth checking out. Make sure you rent the firearm for her to test at he range before picking which one she wants to get. Some people don't realize that small firearms are more difficult to shoot b/c there's less mass to absorb the recoil. If she doesn't like the way it feels when she shoots it, she won't go to the range an practice with it. Which means she'll be less prepared in a crazy situation where she needs to use it.
This leads me to my next question, how much firearm experience does she have? If she doesn't have that much experience, then she should take lessons and start going to the range regularly before she starts carrying a firearm. She also needs to understand the legalities of using a firearm, even in self defense