She might find this link instructive. Here's a 50-year-old woman who trains regularly and even owns a Crossfit gym. She's done physique contests before. The before pics are her when she eats 2400-3200 cals per day. Still quite soft and curvy, despite lifting heavy stuff. A body type a lot of women in America would be happy to have.
The after pictures are what happened when she gets serious about diet and restricts calories to 1300-1700 per day. She starts to look more like a female body builder. The difference is in the diet, as both Hallowed and I mentioned. It's not possible to "accidentally" get ripped like that.
Note, the reason you aren't getting more feedback about "how to get my girlfriend to lift" is because if she isn't motivated it won't happen. This question has been asked on behalf of girlfriends many, many times. If she posted the question herself, more women here would jump in to offer advice.
Best of luck.