How do I deal with this situation?

My ex best friend has apparently grown distant from me. I knew it was coming we just weren't compatible but I don't adjust well to change so I had been delaying the inevitable. She however is moving on just fine. She is hanging out with this girl we become friends with in the end of last year. I feel so isolated and awkward around them. A lot of stuff went on and we just grew apart and she has mainly been a bad friend to me but I am just such a dumb person I have a problem letting go. I don't know how to cope with this. We have barely spoken a few words here and there since weeks even months. I know its for the best and I don't want to confront her because she obviously doesn't care. How do I move on? How do I cope with the agony and feelings of betrayal?