Am I overreacting?

So recently I was talking to and getting to know a girl. We were casually dating and I thought it was going to lead into something serious soon. We have been talking since late October and now it is December and she said she is not looking for a relationship and then says she wants to be casual or we can just be friends. Keep in mind, she didn’t tell me this relationship was going to be a casual relationship when we started talking. She asked me on a date and we have kissed several times. I am angry because that isn’t at all what I wanted. I am 19 and she was my first kiss and I have never had a serious relationship ever. I haven’t dated anyone. She is 7 years older and I think she was wrong to keep me in the dark for so many weeks.

I told her I didn’t want to be friends or be in a casual relationship. I told her that other than coworkers I didn’t want to be associated with her. Was this over reacting and was I too harsh for cutting her off completely?