My friend doesn't understand me.?

I won't say real names, but I will explain. One of my friends (lets call her Carrie) is sorta-kinda mad at me.My other friend (lets call her Amy) is a brat, but around Carrie, she acts all nice. I try to tell Carrie, but she says she isn't being mean and that she doesn't do those things. I feel like me and Carrie's friendship is growing apart because of Amy. I WAS Amy's friend, but now it's so grown apart, half of it's in England and the other half's in Australia. Amy acts mean and bratty, but when Mackenzie's around, she turns nice and she's pretty much 2 faced.What can I do to heal the relationship of me and Carrie?