Is it normal my gf doesn't care if other guys see her naked

My girlfriend is gorgeous and is close with many of my male friends, including the 6 guys I live with. She was close friends with some of them before I was. She's often the only girl hanging out in the group. Long story short, she is very comfortable with her body being exposed in front of them and I don't want to tell her what to do with her body. For context, we're in college. This is a list of the things that she's done which are questionable in my opinion:

-She rarely wears underwear in general, and if we're hanging out with my roommates on a weeknight or something, she'll hang out in just a big t shirt with no panties and makes no effort to make sure her vagina doesn't show. She'll cross her legs on the couch or bend over in front of them and her vagina and butthole is showing on a regular basis.
-our friends have a hot tub and twice she has gone butt naked as the only girl in the tub full of guys. Having full conversations with her boobs showing in the tub and then got and and walked around naked for a while afterwards, never covering herself
-there is a picture floating around of her and her best male friend from home posing naked after swimming, she is full frontal and he has the most enormous penis I have ever seen. All of our friends have seen it.
-she wears g string bikinis if front of my friends and lays on her stomach, and her butthole completely shows

She really isn't a slut despite how this seems. She only does this with guys she trusts and I knew her well before we started dating, she never slept around. Just confident and enjoys showing off her body which she has admitted to me. Honestly a lot of this stuff turns me on...idk. has anyone else been in a situation like this, is it normal?