I empathise with you, Gingergirl. I had a similar thing happen to me, and I was so upset about it that I spent several sessions of therapy (where I was going because of depression) on it! I just couldn't understand why a friend of such long standing suddenly seemed to be blowing hot and cold. The particular bugbear was changing long standing arrangements that she had initiated because 'something' had come up - it seemed my time was not valued at all, and any other activity was a better option than seeing me. This wasn't great for my self esteem.
Over time, I started to see that she was possibly someone who liked to have a very wide circle of friends to make her feel secure, and although to me she was a very special friend, to her I was just one of many. And she would spend a bit of time on the friendship every so often to maintain it to the level she enjoyed, but it was rarely a priority to her. I found this quite hurtful and hard to deal with, but once I'd got used to the idea, I wound down my own levels of commitment, and if she changed an arrangement to fit round other people, I would say I didn't want to come if it didn't suit me.
We are still friends, but I think I'm more realistic now, and have come to terms with the fact that this is just how she is.
Is it possible to remove a topic from "I'm on"
Terrible relationship with DIL - am I the problem?

