After you've tried communication and compromise, being very firm about it being over- no calls, no texts, and sticking to your convictions works. You will receive a slew of harassing calls, texts, emails but they will eventually subside.

I had to do that with a friend I had since I was a kid. Her over the top kookiness is what drew me to her. She was the funniest person I have ever known. Totally obnoxious person, yet it made me laugh. There were several times I had to take a break from her, not speaking for up to a year or so. But later in life, she got much worse, her life a train wreck and her toxicity toward me unbearable, so I really had to end it. She still occasionally texts and emails me acting like we are still friends and I do not even respond.