There are 102 Quadrillion Unique Characters in Brink. None of them are female.
I've said in the past that diversity is expensive. More expensive than most people realize. You can't just take a few clothing options away from the men and find yourself with enough development resources to build a female character. A female character is going to require an entirely new model, voice files, different behaviors for the sliders that shape her, all new clothing models, totally different hair models, different hitboxes, and totally different viewmodels. (Viewmodels: The arms you see in front of your face in a first-person game are usually separate models with different animation and rigging.)
So, doing two models instead of just one is more than twice the work. There's all the work for making the men. Then you have to do all of that work again, because none of it can be re-used for the women. Then you need more work to ensure the models are balanced against each other and inter-operate properly.
It's hard. It's expensive. I understand. But it's still incredibly strange to see a game in 2011 that lacks such an obvious and fundamental option.