My friend is rude...?

I have been friends with this girl since kindergarten and we've always been nice, honest and supportive to each other. I've always had other good friends, but this girl was my best friend forever... sort of. Things have started to change last year over the summer holidays. She met some new friends and she started to hang out with them often. When the summer holidays were over, she was totally different. Since then, she has been so rude and straightforward. When i got a new cell phone, I didn't brag about it. But when she saw it, she said something like ''You have a new cell phone? Whatever, my cell phone i so much better than yours.'' When she got new shoes, she was bragging about it all the time; ''Look at my new shoes! They're so much prettier than yours! They have a beautiful flower print! Your shoes are so ugly, and the golden detail will fade with time. Your sense of fashion is horrible.'' The truth is, she has no sense of fashion. Everybody says that, but they are afraid to tell her. And when she heard other people saying that my clothes are nice, she said something like ''Whatever, my clothes are more expensive than yours.'' or ''If you buy sneakers, buy nike, not reebok. You have probably heard that a lot of famous people promote reebok, so you're trying to be cool, but don't be a copycat because it is miserable.'' She has also started to insult my favorite types of music. If people say I'm pretty, she says me she's much prettier than me, more popular, etc. I just can't stand it anymore. What should I do?