My ex is getting on my nerves what should I do with her?

My ex girlfriend dumped me a year ago because she thinks that she's too good for me:). 4 months later she asked if we can be just friends I said okay.
After a couple of weeks I was talking to her and I was feeling quite down. She asked me why and insists that I should tell her because we're friends and she won't judge me. I told her that I have a problem with my new girl because I wanna marry her but she thinks that we're still young.
She tried to make me feel better and we changed the subject quickly.
Few days later she sent me a long message saying that I'm not loyal and tons of insults and again that she's too good for me, and said how heartless I am for telling her about marrying my new girlfriend, like what the heck she asked me to tell her my problem and insisted!! And dumped me again as if I was her boyfriend.
Now she's writing bad things about me and my new girl on her social media and blame me for everything. Sometimes she writes things like I want to kill him but doesn't mention names so I can't take it to the police. I'm a night person and she knows that so now when people ask her on social media about whether she's a night or a morning person she replies things like: whoever say that they're night person they're lying because we're all morning people.
It's annoying when she writes about me like if I was the bad guy (I didn't stalk her but I see her posts on my timeline).
She's the one who dumped me and insulted me.
I hate her so much she's giving me no choice but to stop her dirty tongue forever.
My ex is getting on my nerves what should I do with her?
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