What just happened between us?

This girl and I became friends about two months ago. There is definitely some chemistry between us but neither of us ever made a definitive mood to hint at anything more than friendship. In the past month we've hung out about six times, just the two of us. Two nights ago we went out again just for some drinks then I took her home and when we pulled up to her driveway we started talking in my car. She was asking me how I felt about her and I told her that I really liked her but if she just wanted to be friends I was alright with that because I respect her. She told me that she really likes me too but doesn't think it would be a good idea to start anything serious because she starts grad school soon. As we were having this conversation we kept getting closer and playing around and as I started to tell her that it would hurt to not be with her but that I'd be alright she told me I smelled really good and started getting real close to my ear. The next thing I know she starts kissing my neck, we end up kissing and then we start making out. Eventually she had to go but before she did she gave me a really long kiss then told me to take a day and think about everything. It was amazing but at the same time I'm not exactly sure how we went from saying we should be friends to that. What just happened?