How do I get my ex gf to leave me alone?

[Dwayne]

We dated for 3 years until she left me for someone else. The beak up was civil at first until she started spreading lies about me, so I cut al contact with her and decided to move on with my life. About 7 months later I found a girl I really liked. The day we started dating my ex added my new gf on fb. Then was saying mean things about her to my freinds, saying "I downgraded" and shit. Which basically lead to us breaking up a few months later. Now the other day my exs best freind followed me on twitter then after I accepted it unfollowed me. Obvious sign she is having her freinds snoop. Why tho? I just want her to leave me be. Then I heard from a mutual freind that she was saying that one day she wanted to see me again. I don't want that. She is still dating the guy she left me for but still stalks my shot. Why?