Am I the Asshole for breaking up with my girlfriend?

I'm 23, and my girlfriend is also 23. We were in a relationship for two years. She had a habit of stalking her ex-boyfriend. I confronted her about it, and she promised to stop. However, she continued to do it. She claimed that just looking at his pictures wasn't a big deal. I suggested that she would feel the same way if I did the same to her. I decided to break up with her. It's been 24 hours, and I've already received 152 calls from her. I don't know what to do.