Ask about things you are interested in or curious about. It's not necessary to ask questions in order to present yourself in a certain way, unless this is an interview -- and even so I'd stick to genuine questions.
I'm spending it making a pros and cons list for Yale, Harvard, Stanford, Full-ride Columbia, Chicago, and NYU, fully knowing it will soon become a useless file.
Well I'm pretty sure they don't admit anyone that they don't interview so it is a good sign in that respect. Congrats and don't sweat it... You're an intelligent woman and speak well... Just be yourself and you'll be fine. Good luck!