Velobambina, since you're in the DC area, I'd suggest you go to The Bike Lane in Burke to see what they've got and to talk to them. Also check out their Buyers Guide to Mountain Bikes. They seem to know more about mountain bikes than most other LBS's in the area that I've been to. I took a mountain biking clinic from them last spring, and they sponsor a women's team, so they're very familiar with women and MTB's.

(And when you get that bike, please join the rest of us in the TE-Mid-Atlantic forum for our occasional rides in Rosaryville State Park.)