The worst thing that could happen is not being rejected. Just one hypothetical worse case scenario is:
1. Being accepted, signing over equity and giving up on the chance to move to another accelerator.
2. Getting to YCombinator and realising that all of the group bonding indeed happens over heavy late-night boozing sessions.
3. Trying to find a way to remain part of the group experience without participating in the boozing, but failing and becoming disillusioned and demoralised.
4. Abandoning your startup because you can't join another accelerator anymore and are afraid having to explain why YCombinator didn't work for you.
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).