<human>: I [M21] am a little uoset that my gf decided to go to a party and is now deciding to sleep on some random guys couch who I have never even heard of until just today.

A little backstory: Me and gf live in two different cities and none of us drive (I have a fear of being behind the wheel and she is still learning how to) and we only get to see each other on weekends. Well we didn't see each other for 2 weeks because of different family things and after talking about how much we miss each other decided to announce she would be going to a party with some guys that are friends of her cousin.

Now today she is at the party and announced she will be sleeping on this guys couch. I have never met or heard of these people before until just a few days ago. After saying I wasn't 100% sure i'm okay with this I am now being ignored

I'm a little upset but do I have the right to be? I mean we have only been dating for 4 months now. I'm upset but is this rational for me to be upset? What should I do?

Could you distill the essence of the text into 1-3 sentences?
<bot>: Gf of 4 months is sleeping on some random guys couch after choosing to party am I in the wrong to be upset and if so what should I do?