I get like that sometimes. I blame girl hormones for that. Theres a couple things that could be happening. Either she's having second thoughts about the relationship or its just "one of those days."
Since she text'd you back and said sorry, I think it was just a bad day for her. It happens. As long as its not a constant and consecutive accurance then I don't think its anything to be to worried about. Maybe she's stressed over work/school. Could also be PMS issues too. Theres many underlying and confusing factors to women.
Evil School!!
May not be on LF as much, due to unforeseen circumstances.
Blame College and Homework for Everything!!
-Fawn