Your friend could just be a really independently-minded person. I know I am like that a lot. I prefer time to sit and think and work through a problem in my head. Having other people around just makes it harder for me to think it through. Maybe you should send her a casual note, text or email and ask what's up. Just be direct : Are you avoiding me or do you just need a lot of time to yourself? If it can't be worked out, and it's really upsetting you, you may be better off without that friendship, as others before me just said.