Basically some other women will often be just as discouraging and as sexist as some men. They will reinforce the same strict gender stereotypes for the same illogical reasons as the men.
What if they are just voicing their opinions?!?
I had a girlfriend that was very "stereotypical" - I practically had to beg her after every meal no to go to the kitchen to clean up, but to stay with me at the table and just talk and relax. Is she wrong by being who she is, just because she is "reinforcing illogical stereotypes"?
People are different. Be yourself, hang out with people who accept you for who you are. Let other people be.
Your girlfriend was probably quite satisfied with a kitchen that had been promptly cleaned and that made her happy. However if she ever voiced the opinion, 'You should help me clean up', to your younger sister then that wouldn't seem okay to me.
Maybe women perceive men as being sexually discriminating because they only receive sexual comments from men. When I try to think about it, I (as a man) also receive much more sexual comments from men. Maybe it is simply that men are much more open talking about sex, and when we do it with everybody, men and women alike, but when women hear it, they think it has something to do with them being women...
I don't know if I'm correct, generally, but in my social circles, we joke about sexual stuff a lot. (With friends, of course, not at workplace.)