This girl bullied and ruined my school life and I want her dead. I can't function, what should I do?

Whilst I was at primary school I was bullied by a girl, it eventually stopped until I became best friends with her through high school and it started again, but got so much worse. At school, she turned it around and the teachers believed that she was actually the one being bullied by me. I don't want to go into detail but it has affected the way I am today and even made me clinically depressed. 2 and a half years later, she is really happy and has a really nice boyfriend and I want her to be miserable like she made me. She gets everything she wants and it's really bothering me that there seems to have been no revenge. I know revenge isn't the best answer but it would be the only thing that would allow me to move on. I actually want her dead, which is such a bad thing to wish upon somebody but she made me feel as though I was better of dead at times. It's really getting me down, what should I do? I cant avoid her because I see her in college everyday.