<human>: We've been dating for almost 2 years now. She is very loyal, very trustworthy...however, when she hangs out with a group of her high school friends (a group of about 3 guys, one of which is her ex) she never invites me along. She says its healthy to do things apart and she just likes to have fun. With these male friends, she has done the following:

1. Gone skinny dipping at a "pitch black" lake 
2. Had her ex hit on her with an alleged plan of getting her drunk and making a move (not her fault)
3. Shared a bed with one of the guys (nothing happened)

They also have played stripping drinking games together, but not while we dated. She's apparently been down to a sports bra and underwear. 

She insists they are, and always will be, only friends. They've been friends since they were just children. I've gotten pretty upset about this stuff, but ultimately I know she would never cheat on me. 

Is it wrong for me to get angered by this stuff? Are her and her friends very inappropriate? How should I handle this - should I insist on her not hanging out with them, or is it not a big deal? Thanks!

Could you distill the essence of the text into 1-3 sentences?
<bot>: GF and I have been dating for nearly 2 years. She is questionably inappropriate with her group of male friends. What should I do??