How can I get my girlfriend back?

I don’t have time to explain the ray of emotions that Krista made me feel. In laymans terms, I was in love with her. I lived and died for her. I wrote her cute notes every day and called her every chance I got. I ran to see her between all my classes and hugged her so many times even now I can remember her scent… The fact is.. I loved her.. but she apparently didn’t love me as much… we dated for eight months… When we broke up.. a week later she got a new boy friend… It was her ex… It’s been about a year now and I still cringe when I look at her. I miss her.. I love her.. but I hate her for what she did to me. I stay up some nights just crying about what I lost… I see her every day in theare arts class and It's kills me to look at her and know she's not mine anymore. How can I convince her to break up with her bf and go back out with me?