In fact, is it even tzanuah for the girls to be here?
Why would the onus be on the girls? You think it isn’t tznius? So you leave.
As my mashgiach said when someone suggested the women should come through the back door of the yeshiva on shabbos: you could go through the back door.
As to the actual question: I think it is mostly ok, since we don’t know who each other are and there is no way to contact anyone for real. But if you feel like a comment you are going to make is innapropriate–then you shouldn’t make it. And if you feel like the “relationships” you are getting into here are innapropriate–then you should leave.