Blueberry, that sounds awful. I am on the Luna Chix email list, too, but I have never gone to a ride because I suspected stuff like you described would happen. I am probably too slow for them now, anyway!
I hate that "helpful/condescending" attitude. Like when people yell, "good job," to someone who is struggling up a hill or just near the back of a ride. To me, it has always meant "Good job for a slow/fat/old person." There's a variety of reasons an experienced rider may be at the back, so now, if I am checking in on someone, I do it with a humorous comment. Of course, I have been on the receiving end of this many times and I want to scream F-U.