How to stop thinking about an ex that broke your heart?

So yeah long story short..I was seeing a girl for about 6 months and she dumped me twice. The only reason I got back with her the second time was because I fell for her BS lies. I can't stand it but I think about our relationship every day. Since we've dated, she's been with 3 other boyfriends...and I haven't had any new partners. I just wanna know a few ways I can just flush her out of my mind and my life completely. I've ignored her any time she tries to communicate with me and haven't spoken to her in a couple months but it's just not doing it. I'm not going to change that but there must be other things I can do. I've overall been very happy with my life..but it's just one of those lingering things in my memory/mind that won't go away.