i just want to say that just because you're female you do NOT necessarily need a women-specific design. None of my bikes are women-specific, and they're all stock sizes, not custom.
from what i understand of the WSD (women specific design), it's designed for people with shorter torsos & longer legs. Which is the complete opposite of me.
If you really want to buy a bike, i highly suggest that you go to the local bicycle shop. They want to help! Cyclists HATE to see people on ill-fitting bikes! Tell the shop how much you want to spend and they'll go from there. Some shops even have rentals. My LBS does.
i can't give you any advice about tri's, but i suspect that the other posters are right & you'll see bikes at every pricepoint at your race.