Considering she's so withholding with information right now, my guess is that there probably was something inappropriate with someone in your circle of friends.
That's what I read too. Look towards someone very close.
EDIT: Someone that she thinks that if you knew would be a deal breaker. That and her conscience bothering her that you would consider her a tramp.
Last edited by Gnosis; 12/22/0910:49 PM. Reason: added a sentence