@marysan,
The most obvious thing to do is: block her phone number, block her email account, remove her from 'friends' in your social media account, and perhaps make it so only friends can contact you...then most of the communication you don't want just doesn't happen.
Other methods -depending on the laws in your area, there are several things you can consider:
Civilly:
- restraining order / no contact order / good behaviour order etc
Criminally:
- harrassing phone calls
- stalking
If you must talk with her, take some courses in / read some books about:
- dealing with manipulative people
- communicating / difficult conversations
- assertiveness
An in any event...it's very unusual for a person to still hang on to resentment 6 years on. It's something that stays detrimental to your quality of life for as long as you hang on to it. If you have not seen a counsellor about letting go, and finding your own happiness again - I hope you consider it.
Best wishes.