One reader has kindly, and politely, emailed me to tell me he's totally alienated by her immoral behaviour and isn't going to read any further! And judging by the dip in the scores he's not the only one.
Since the scoring indicates this is a broad response, maybe you should rethink your 'sexist' accusation. It sounds more likely that the readers didn't find the character's response 'in character', rather than thinking that 'girls don't behave that way'. After all, this is porn, and everyone knows that girls are going to mount anything that moves in pornography!
I'd suggest you go back and review both the chapter in question and the character, and see what the readers are seeing that you aren't. (And don't pay too much attention to what they say. I often find, readers will complain about one thing, but if you can get them to expound, another issue comes out, not-directly related to what they initially complained about. Typically, it's these other issues were are more essential than the ones they stated.
Good luck tracking down the issue.