It's easy to take it personally, but people change.
Can you think of anyone you don't feel the same about because you're lives are so different now? It's not necessarily anyone's fault or mean she can't stand the sight of you, you're just not 'compatible' in the way you were 10/15 years ago.
Have any mutual friends given any clues as to what's going on?
It could be totally innocent though, she genuinely might have trouble finding the time to see you and had a specific reason for seeing the mutual friend but not you.
Do you like her is a good thing to start answering whether to give up on her or not.
I'd send a Xmas card and then leave it unless you'd like to find out what happened for your friendship to change. If you're not bothered either way I wouldn't chase it.
If you do want to carry on the friendship I'd give her a call and say something like "hear you're catching up with friend A tomorrow, I'd love to see uou next time you're in town...., when are you back?
Hmmm mumsneting drunk, was not a great idea. Don't feel quite so angry now. still I'd like to put this to the jury. It's one of those things where I've made effort after effort and I'm not sure why. She just isn't that bothered about her friends. She has a few close pals who she tries to see including the one in my town. The rest she doesn't bother with.
I guess im just hurt at all the times I've tried to keep in touch and all the times she's not tried or made rubbish excuse. Usually I'd text and say "hear you're in town would you like to grab coffee" but as shes not bothered to mention it to me I already know the answer. For some reason it's usually me trying to get in touch with friends and not vice versa. It makes me and feel like I'm an awful person.