I'm going to a party behind my gf's back.
Why do you need to sneak around her?
I think it's pretty normal for an adult.
I get that part of being an adult is doing whatever you want, but you have a responsibility now. Your girlfriend is a huge part of your life and you can't just treat her like background noise. You are supposed to be in a meaningful relationship, and not telling her where you're going can lead to a lot of anxiety and distrust for her.
That's true. For the time being, we'll have to break up to do whatever the fuck I want.
That sounds sad you want to break up. Don't you think it would be easier to tell her you are going to a party? If you think she is too controlling I guess that might be for the best.