She told you about being demeaned sexually by other guys to get you thinking about her sexually. Those guys don't bother her because she doesn't really care what they think and they have a pre-existing relationship. But she doesn't want to you to sexualize her because she wants you to see her and treat her as a respectable upstanding woman. When you sexualized the dynamic, it made her feel demeaned in a way that the other people didn't.
Sort of like telling your boss about how you and your boys joke about banging each others wives and then your boss makes a joke about banging your wife. If you're not prepared for it, it can seem like your boss is crossing a line that you haven't let him cross yet. Yet to your boss, the fact that you mentioned it at all seems like the line has been crossed.
So, it's a misunderstanding based on perspective. She doesn't think she opened the door to that type of joke but you do. Honestly, I agree with you but I understand how she doesn't.