hurt feelings

It's amazing to find that someone who you haven't seen in a year can still reduce you to tears. I found out yesterday from my husband that a former friend of mine was more comfortable sharing her life and problems with him than with me. This is a girl who I used to consider my best friend in the entire world there is nothing that I wouldn't have told her. And I once thought she felt the same about me. And then it comes out that no she didn't. She couldn't trust me with her family secrets but she could trust my husband whom she was close friends with for about oh...3ish years. Apparently that trumps the 18 years that we were supposedly best friends.
I don't even know why this still hurts me considering we haven't been friends for almost a year now. My husband is a good man and he's still kept his word to her and kept her secrets. And honestly it wasn't not knowing what they were but the fact that she just flat out didn't trust me. That's what hurt. This woman...someone who was supposed to be my friend, my sister. The girl who grew up with me. We were going to go to college together. I was her maid of honor. She was my unofficial matron of honor. I hosted her baby shower. How do you have a relationship like that and still not trust the person? I'm not saying I need to know all her family's closet skeletons. It just hurts to find that when she needed to talk to someone she went to my husband, not even another life long friend (I know she has/had 2 or 3 besides me). If it is so painful so secret how can you share it with someone you've only known 4 years but not the person that has grown up with you and shared so much with you?
What did I ever do to make her not trust me. What happened that a relationship like that can end so suddenly with no real rhyme or reason.
I don't think about her often but it's shocking, or maybe not considering how I felt about our past, about how painful it can still be to know what she thought about me and how she felt about me.