I want my girlfriend to get rid of her cat
Why do you want her to get rid of the cat?
I want my apartment to be flea-free
You don't care for cats because of the fleas, but your girlfriend would be unhappy to choose between the two of you. You don't have to like anyone's pet but if you make her get rid of it then she might get rid of you instead. She has the right to keep her cat and break up with you if she is attached to that cat like she should be.
I don't care about you and your stupid ideas. I'll get rid of you if I have to.
If you truly care for your gf you won't ask her to get rid of her cat.  You should focus on keeping the car clean and healthy. It won't attract fleas.