I have been the toxic ex-girlfriend.

Block her number on your phone.
Unfriend her on social media.
Do not answer her emails.

If she shows up on your doorstep, tell her you will get a restraining order. Follow through if she does not leave you alone.

You are better off without the emotional blackmail. That's what it is - emotional blackmail. Even being alone is better than being her puppet. You can love someone else, someone better than her. Love yourself. Cut her off and live your life.