Either coolest girlfriend ever or she's gonna ambush you when you actually go through with it.

You may want to hide any guns, knives, baseball bats you have laying around LOL.

either she has something nasty planned for you  or there is something else fishy going on.  If she really dug you being with other girls she would at least want to watch or be involved, not sitting in another room.  Furthermore how would you make this work with Hotel incall?  Outcall I can see, but even incall at an apt setting most would not be ok with it because who knows what that chick is doing in the space.  She could be robbing the place, looking for $ because she is someone we are unfamiliar with.  Not to mention if a lady considered this she would need to be screened as well, not just you.

I would seriously reconsider this, and maybe just pick up end of the night civi stragglers at the bar with her instead.

another room?

maybe she is into audio-voyeurism....

I like it!

I have had encounters with my husband where I did not necessarily want to get involved... or even where I was present but purposely ignored.. or fucked ON TOP OF with no direct attention to me.  VERY FUKKIN HOT!