Well, that's not actually true, because she didn't apply to yc to begin with, so we don't know whether or not the choice would have been available.
Oddly enough, I think I met ericabiz (hello ;), she briefly stayed at my house through airbnb. I totally agree that she is talented, and that if people like her are not even applying because of such a perception, it is a problem. I feel it's a false perception, but not well-addressed by statistics trying to prove or disprove a lack of bias (as she had suggested).
But, really, it's a one page form and it was designed to be useful for founders whether or not you are accepted. The worst outcome (which 95%+ of applications receive) is not getting an interview. So apply! (erica and every other female, male, white, black, green, 40-something etc in this thread).
Fear of rejection (not just from YC) is simply a dumb fear if you think about it, particularly if your doing a startup. Because you are going to be rejected over and over anyway, and ultimately no one can save you from building something no-one wants (the only rejection that means anything in this context).