I need to let it go.

There is this thing that I need to get over. Something that needs to be put in a room marked 'The Past' and locked up forever. I can't seem to do it though. I think much of it has to do with the fact that nothing like this has ever happened to me before and it involves a close relationship that I had (or so I thought).
Amy was my one of my best friends. We met about 10 years ago at the place that I currently work. We had very little in common, as far as where we were in our lives, but much in common with our personalities. We're both silly, love to shop, love to overeat, and the list goes on. So we became close friends in a short period of time. Long story short (in the course of 10 years), she moved, we remained close, I chose her to be Emma's godmother, she fell in love, got engaged, asked me and my girls to stand in her wedding and this is where it went bad. This was earlier this year. She, apparently, expected me to attend most of the pre-wedding events where she lives in Houston. It wasn't feasible for me to do so. In a matter of a couple of days, she literally cut me out of her life. She would not answer my phone calls, even after I begged. She refused to talk to me. She sent me two emails basically saying that I had been a horrible friend and I was making her life, at the time, miserable. She told me she no longer wanted the three of us to be in her wedding and basically ended the friendship.

Just like that.

I was completely caught off guard. I had feelings that I can't even explain. I questioned every other relationship I had; with Mark, my mom, my sister, my friends, my co-workers, almost everyone. I wondered if they perceived me the way she did. When I say 'questioned', I literally questioned many people to find out how they felt. I told them about comments she had made and how these comments seemed to come out of nowhere. Everyone told me that it sounded like issues on her part, and that the person she described didn't sound like me at all. I know she has issues, I always have, but I just never realized that these issues would cause our friendship, in large part, to end.

I should be over this. I haven't talked to her in months. I tried to write to her and explain things from my point of view. She didn't respond. She has obviously moved on. If she can, why can't I?

I've always been the type of person that doesn't like conflict; I don't like people to be angry with me. She is angry and there's nothing I can do about it. And it makes me nuts. I even have dreams where we reconcile our differences and it's such a load off of my mind when we do.

I've decided that she's done and said such hurtful things, that I could never remain friends with her. I have no desire for her to be in my life, or my family's life. So, why can't I let it go? Is it because of my general desire to be liked? Is it because I lack self confidence and need approval from others? Is it simply because I'm nuts? Whatever it is, I know I need to move on. I'm just not sure how to do that.