I think you should just send her an email saying that you are sorry you bothered her but that you called out of genuine affection and interest in her. Then tell her that since the past several years, you have only gotten a defense or angry/upset response from her when you have tried to reach out, you will distance yourself from her and stop bothering her.
However, be sure to leave it with the thought that, "But if you need me or want to try to reconnect, please let me know. You are a dear friend and I care for you and want you to be happy."
And then just let it go. If she has not been able to overcome whatever it is that is causing this defensive/angry behavior, there is really nothing you can do. Continuing to try to be friendly and getting verbally slapped in the face is just not worth it, imo.
From what you're written, it really sounds like she could use professional counseling. If you have the guts, and tact, you could suggest that, but otherwise, I'd just send the email and let it go.