I'm sorry to hear about your friend. I don't think you are being selfish, and its understandable that you are hurt, it is your wedding after all. I can understand her not being able to make it with the whole camp thing BUT she should have at least called you and told you what was going on instead of making you wonder.
I had a friend that I did EVERYTHING with for two years, she met her now husband and basically disappeared of the face of the earth. I was in her wedding and spent a TON of money to go (it being very far away). She got married in 2007 and I have litterally hung out with her 5 times since (she lives 15 minutes from me). We still talk from time to time but I've kind of cut my loses. There were enough instances where I would feel hurt that I decided that it wasn't worth being friends with her anymore. I'm not saying that you should do the same but I'd think about who you really want to be friends with. I have very few friends but the ones I have would do ANYTHNG for me and are there for me no matter what. Just my thoughts but I don't like to see people upset.