Thanks for the excellent article. There are two separate issues here. One is that people of the opposite sex often mistake interest for sexual attraction. I don’t think this is particularly sexist as it happens both ways (I have had it happen to me). But the other is the fact that people assume that a woman who is socially outgoing is using sex to get ahead. That is horribly, horribly sexist.
Years ago, I taught classes at a local graduate school, and one semester the woman I had been living with for five years took the course (before anyone makes any assumptions, she was actually slightly older than me). Before I let her enroll I told her that if she didn’t do best in the class I would flunk her because she had an unfair advantage and I wanted there to be no hint of unfairness in grades. But it was not widely known that we were a couple. About 3/4 of the way though the course, I was at an event and some of my other students were there, and they (cautiously and concerned) asked if I was having an affair with one of the students in the class. I laughed so hard!