How do I get her to stop talking about me behind my back?

We used to be friends. but she stopped talking to me. like would roll her eyes at me. I asked her what was wrong and if I did anything to her; giving her plenty of opportunity to say what was on her mind, but she just said “sometimes I just feel like being quite”. I gave her some space and we just stopped being friends now she is talking about me. she tells someone I made her mad at dance class because I talk too much in general just like everyone else and not even to her. thats honestly petty. like I don’t have the privledge to talk in her domain. Pssh girl please. but what really gets me is that she talks about me having acne and how I try to cover it up with makeup. she knows how sensitive I am about my face. I know shes no friend of mine but I want her to man up and step to me. I can’t just let her keep talking about me; it hurts me and some things you just can’t ignore. How do I handle someone like that?