13f-
My wife is the same size as your girlfriend, maybe even an inch shorter. I was sure I had all the answers. I figured my Glock 19 would be perfect. Low recoil, small size, etc. Well, it was too thick for her to get a good firing grip. Surely, my P7m8 was the answer! Well, she found it hard to cycle, and she hated the squeeze-cocker.
Remembering what Col. Cooper once said, I handed her my Kimber Classic .45ACP. Well guess what? She LOVES it, and now refers to it as "her gun" (be careful what you wish for!). I didn't tell her about all the grown men who whine about the "bruising recoil." Please!! She loves the nice trigger, sights, etc. She can cycle it herself. You REALLY wouldn't believe the groups she gets. 7 rds in one ragged hole @ ~7 yds. Not bad for a beginner.
My wife didn't like the revolver, except in single-action. Remember this, new shooters like to be successful. They don't want to drill and drill for months. By then they'll give up, oftentimes. Start her up close to the target, and work on the PERFECT sight picture and SURPRISE trigger break.
The only thing I did to my Kimber was replace the grips with thin rubber grips ( $10 @ Brownells), and I actually like it better. Hope this helps, feel free to eamil me if I can be of any help.