The youngest of us is 18 and the vast majority are within 23-40. The people involved and myself, we are all grad students. I don't have time for a full detailed answer right now, and I'm not even sure if "the rest" is of any importance. But I'll just say that things like this are not uncommon in the dojo. It simply took me a while to see that something is really wrong here.
That sounds like it's pretty messed up, then. I'd be moving on.
This is probably completely unrelated...but at your new dojo (assuming you move on to a new place), before referring to an adult female human being as a "girl", you might ask yourself if it would feel appropriate to call an adult male human being of the same age a "boy". Context is everything, of course, but calling a woman "girl" can come across as dismissive or disparaging even if that's not your intent.