The Truth at Last

Several months ago I had a falling out with a "friend" that I had a relationship with for some years. I thought that we were close. I thought that our friendship could weather disagreements and differences of opinion. I was wrong.
For the longest time, I acted like her words and actions didn't bother me. I was so busy I allowed my work to distract me from what I was feeling which was disappointment, betrayal, and anger. I held these emotions in for months. I never really aired them to anyone, other than to her - my sister, my "friend".
It all started with a poorly worded post in a social networking site that I administered. The bruhaha and the subsequent fallout escalated and escalated until there was no room left for friendship.
How can a person possibly have any type of relationship with someone who leaves no room for any opinion but her own? How can one have any type of relationship with a woman who used fake "identities" on said social networking site to personally attack and malign them? How is it possible to turn the other cheek, look beyond the betrayal and try to understand another point of view? Well, the answer is I have forgiven, I do try to understand her bitterness and anger, but there is simply no room for any type of friendship left. Sad, isn't it?
This was a woman that I spent several hours with on the phone every week. This was a woman who, if she called me in the middle of the night for help, she could expect to get it. This was a woman I respected and trusted and now, this is a woman that I have no contact with whatsoever.
The things that she said about me were not only hurtful, they were LIES. Flat out lies. After everything that is the one thing that I just couldn't get beyond.
It still makes me sad, the loss of this friend. I think about her and wonder how she is, but deep down, I realize that no relationship can exist without trust and frankly, after everything, I could never trust her again.

This brings me to my current situation. I left said social networking site, in no small part due to the poison and the lies. I joined another site - Facebook - and I love it there. For the most part, I am friends with people that I genuinely care about - people who I want to keep track of and be a part of their lives. There is one individual there though whose friendship I accepted and now I regret. She was party to the events described above and though she did not actively participate in the lying and maligning of my character, she appeared to be cheering on the sidelines during the worst of it.

I want a fresh start. I do care about this second woman, but I'm unsure whether I am capable of offering her true friendship based on all the hurt and betrayal that I still feel. Any words of advice?