What to do about this ex-friend?

Hey, so for about a year I have had problems with my ex-best friend. We used to be absolutely inseparable, and we had a falling out. Now she is totally obsessed with me. I'm not saying i didn't do bad things to her, but she has done much worse to me. She has told people lies about me and talked about me constantly for the last six months. I know everything she says because everyone tells me, and she knows I know, but I do not retaliate. She tells her little friends things that I "said" about them and then they go along with her. I basically backed off and left her alone after a couple of weeks, because it was almost funny the way she was about me. Soon after I realized she was cruel and gave me a reputation of being cruel, too. I think maybe she realized how much she needed me, or maybe jealous about how easy it was for me to let go of her. But she has made a lot of people hate me, and spreads lies and rumors. She even told the lady she babysits (well, not anymore. We did it together) for that I stole money from her house while I was there, so she would fire me. She ended up getting fired. Lots of stuff like that. Help, please!