I'm being bullied my my ex-friend?

I told her Wednesday that I no longer wanted to be her friend, and ever since then, she's been mean and harassing toward me. She's insulted my dancing skills, which she knows I'm sensitive about, she's gone onto my dance group's channel and basically pointed out every little flaw. She says that she can do this because she's 'an experienced dancer', and apparently knows everything because of that. I've told her to keep her nose out of my dance groups' business, and she just flat out says no. I have put up with this harassing at school, and over the internet. I don't know what to do, besides move to Antarctica, and live with penguins. Help is appreciated to NO end!