I have a question on how to deal with an ex and best friend?

Okay, well I have two people kind of doing the same thing to me, generally speaking, So my friend and are recently over; I tried to end it tree times but she likes to think she did because she agreed the fourth time. But now she's telling lots of people stuff that's not true or my secrets. So now she's ruined my reputation and three of my other friendships. She twists my words and makes me seem like a bad person, which I'm not. What should I do?I have a question on how to deal with an ex and best friend?
Well don't care about her just try to get your other friends back by telling them that wat shes saying isn't true and that its all lies and that shes the one they shouldn't be friends with since shes saying that kind of stuff. Try to set things straight for the people who thinks the rumors are true and if nothing works try telling some authorities like teachers and principles before you can't show up to school because of her.