Me (18 m) and my girlfriend (18 f) been together for almost a year and a half. 2-3 days ago she told me she wanted to go to a vacation for 3 nights, I asked with who, she told me a girl friend of her (which is a great friend) then I was excited about it for her, but like 10 seconds later she mentioned another male friend is coming. I asked if all of them would be in the same room, and the answer was yes.
A bit of context behind that male friend, my gf + 2 female friends (on of them is that female friend) + 3 male friends (one of them is that male friend) went to another vacation for 5-6 nights about half a year ago, I was fully supportive and encouraged her to go, they had two rooms one for the girls one for the guys. About 2 days in she started telling me that he is doing some weird stuff, he said "I would’ve kissed you if you had no boyfriend", and "you are cute\\pretty" in addition he was leaning on her when they played board games. We both agreed at the time that he was weird, even after that she met with him in groups of like 3-4 people a couple more times.
I told her that I felt uneasy about this, but she told me "I’ve talked to him already he knows what he did was wrong" and that nothing would happen and that it is not weird that her, her girl friend and him are sleeping in the same room. At the end she asked me for a firm answer if she should go. I feel weird about controlling whether she goes or not.
Sorry it is so long I didn’t want to leave any context out.
EDIT: Firstly thanks everyone for commenting, I’m reading every comment 🙂
I’d like to say that there is no way I’ll break up with her for this, I truly think that in her view it’s not a relationship killer, and that she means no harm, even though it makes me feel uneasy.
In addition, the female friend that is coming is probably the most trustworthy person I’ve met, even when she’s drunk she’s mother-like, so she probably won’t be a part of a cheating scheme and try to defend anyone, and she is aware of the history with the guy as she was in the first vacation.