She could say that she just doesn't have enough time to dedicate to an actual dating relationship right now in between the sorority (I'm assuming this is the zeta daughter
), schoolwork etc. and that if she was to pursue a relationship with anyone she would want to make sure that she had enough of herself to give.
Something like that-only problem is if she meets another guy she really likes two weeks later and suddenly has the time :P
Also Kevin is right...it may hurt at first but being direct is seriously the way to go. No crossed lines or miscommunication.