Wasted Energy on Hate

I was emotionally abused by someone that was in my life for years. I didn't know how bad it was until we stopped talking to each other and they smeared my name to everyone close to me, it was easily done because I had isolated myself due to an abusive marriage (not to the person I hate) and this person had been very two faced the whole time I knew them. They accused me of being a neglectful parent, stealing from a charity we both volunteered for, being an alcoholic, sleeping with lots of men and being a racist. They stalked me and rang employers to badmouth me. Except for sleeping with lots of men and being an alcoholic, everything else they did themselves and was trying to deflect on to me. Sleeping with lots of men came from me having a one nighter with someone after breaking up with my ex, the only time I had sex during 3 years as a single mum. Alcoholic because I liked to have a drink when the kids were at their Dads, so once a fortnight. I was weak from my ex and had many problems with my kids that i was dealing with at the time so I couldn't deal with what this person was saying and ignored it. Now 6 years later I find myself wasting energy hating her. I hate that its had this affect on me. I hate her more than my abusive ex, why? How do I stop hating this person so I can forget them and focus on my life?