What do you think about me telling my girlfriend to not have a sleep over here tonight. I'm not comfortable with it.
What makes you feel uncomfortable with that?
I won't be able to have sex with her tonight now and those bitches are so loud during those sleepovers.
Being annoyed when you wont be able to interact with your partner because she'll have her friends over is fine but you shouldn't tell her whether she can or can't have her sleepover, even if you're uncomfortable. You apparently spoke about it before but you didn't tell her how you felt so you should probably talk to her about your issues like a normal couple would.
I'd rather not talk about this.
It's important for you to discuss your feelings with your partner. It would be best if the both of you can reach a compromise.