I'm going to ask my girlfriend to save my game before she switches over to hers
How does your girlfriend usually respond?
She acts like she doesn't know what I'm talking about.
It's understandable that you don't want your hard work to be erased due to someone else's ignorance. You should show her exactly what you want her to do by demonstration so that she won't mess up on her own.
That's real helpful
It is completely understandable to want to keep your games saved after mile points. It might help that you can save your game on your own and not leave it up to chance if she forgets.