Emily does a good job of summarizing some of the reasons why it's hard to find women role models in science. A lot of it boils down to the fact that women frequently get judged based solely on appearances, and that the feedback we got often has more to do with how "hot" or "sexy" we are rather than the content of our work.
It's not an inability to accept compliments (although some so-called compliments are really more like harassment). It's that when we are presenting science and trying hard to communicate ideas, it's really jarring to be brought back to superficialities. How can I concentrate on my science if I have to be worrying about how I look all the time? Plus, if you care more about how I look than what I'm saying, I've failed in my goal of communication.
Now, granted, internet commenters are notorious for bringing out the ugliest in human behavior. But it's not just there that this happens. Not too long ago, I found myself giving advice to a graduate teaching assistant who had an unpleasant interaction with one of her students. Can you blame a young woman for leaving science if she's constantly having her confidence in her skills undermined by harassment based solely on her appearance?
Sometimes I think the only reason that I manage to keep the respect of my mostly-male just-past-adolescent class of intro physics students is because I'm literally more than twice the age of most of the them. So, I guess there's a silver lining there, in that if you stick with it long enough, you grow out of being a young woman. But really what needs to be done is to fix the attitudes of the bad actors out there. As Emily says, all of us, men and women alike, should work toward reining in this kind of bullying behavior that is directed at so many women.