I got waitlisted too at WUSTL, and I was considering calling in/sending them additional stuff (spring grades, a letter about why I wanna go there, etc.). Did you end up being able to call someone and ask them about your application? Also, did you e-mail Nanette, or did you e-mail your admissions counselor? Best of luck to you! If you get off the waitlist, I'll try extra hard.
