Dilemma of a Life Time

I think I've been subconsciously putting of writing this post for a while, mainly becaues (as horrible as this is) I don't even want to give this person the satisfaction of writing about her... but none the less... here it is.
I had a friend a long time ago, a very good friend, who was... to be honest I don't know how to describe it. She was kinda like an older sister, but also just a friend. She was a little older, and SO MUCH FUN. I think it was my friendship with her that made me more okay with acting silly in front of people, and not minding what they thought! It was through her that I got to know others of my closest friends (which in the end would really annoy her!) And then the fighting began.
Let me admit.. I had been warned about what she was "really like" before, but from all our time spent together I would never have guessed this secret mean side of her existed! And then. slowly but surely, I began to see this side that everyone has told me about. I can't say exactly when it started, but she returned home for multiple visits, and it began then.. it was just CONSTANT snide remarks and put downs whenever I would say or do anything. At first I thought I was just being sensitive, I do know after all that I am easily embarrassed and upset. But when even the witnesses began to notice, I knew it wasn't just me. It got so bad that I would leave her company crying every time we were together.
AND THEN, what I never expected even after her poor behavior... when tragedy struck, she turned on me completely. She called me HORRIBLE things, and behind my back insulted my entire personality, and worst, my family. I tried to contact her, and she hid from me, so I left an incredibly hurt message on her phone, and removed her from my internet "friends" list. Since that time she has written multiple blogs and messages about how much she dislikes me, and has even gone as far as to say that she wishes she had never known me. There was a time when I would have expected more of her as a friend, but even my expectations of her as a PERSON were dashed long ago.

She has since apologized, and I really don't feel angry at her for the horrible things she said, but never in my life have I been treated by ANYONE the way I've been treated by her. I can say that I have no hard feelings toward her, but I know that I have not completely, honestly forgiven her. My thoughts are as follows... I KNOW I should whole-heartedly forgive her, but I also know that I do NOT need to put myself in a position to be hurt again. (There was a time when our friendship was seemingly patched up, but after only a few weeks she had again torn it apart!) I can not now, and I don't think ever TRULY trust her again.

I don't know what to do. There will be an opportunity to change things in a few weeks, and I know that those close to her (one of whom is also very close to me) would like things to be fixed, but what do I do? I can't act like nothing ever happened, but I also REALLY don't want a big crying forgiveness speech, we did that in the past and it only made it hurt more when she completely forgot it.

And just to add to the dilemma, I think she is about to make a HUGE mistake. She is rushing into something that I KNOW she should stop, and wait... just for a little while before she does!

What should I do? How should I fix things? Do we have to be friends after we fix things? Can two best friends truly just grow apart to the point where they can't be friends anymore? HELP!