Dunno how old she is, but she sounds like a normal insecure teenager to me. People are like that. They lie, and they're mean, just because they're afraid that if they don't, people will lie and be mean to them.
You however, choose not to take part in this pathetic roleplay. Good for you
Neither did I. It's not gonna be easy, it wasn't for me anyway, but at least the friends you have when you're you are *real* friends, instead of number two and three on the list of most popular girls that would actually like to be number one.