I own a Smith & Wesson SW99 in .40 caliber. I love that gun! Guns are a personal preference but that one just fits me. I don't even have to think about aiming because it just hits where I want it to. It's smaller so should fit your girlfriend's hand. My ex had no problem holding it but didn't like the recoil when compared to a 9mm. I have put thousands of rounds through it without a single jam or any other problem. You should at least have her hold one to see if she likes it.

When looking at compacts, I think a 1911 style or any .45acp might be a bit much. All of the .45 compacts I have shot have a pretty stout recoil.