How to deal with a copycat friend?

My best friend is awesome! She's nice, caring, trustworthy, etc. But she seems to be copying me a lot. Sometimes when I say something, she says the same thing as me at the same time on purpose (not a jinx). And I have a couple of original sayings, as does everyone, that she says to people. She's never really had a sweet tooth, but I've always have. Now, she's always saying she likes these treats. I like jokes and stuff, which she's never really liked. But now she's joking and teasing. Once, I wore something nice to school (for once) and the next day she wore a skirt. And she NEVER wears skirts. Before she told me that she'd never wear a skirt to school. On my birthday I passed out cake to everyone in one of my classes, and the next day she passed out lollipops to everyone in one of her classes. When I started wearing my hair in a ponytail (which surprisingly I got a lot of compliments) she started wearing her hair in a ponytail. I've been writing a story for a couple months with 3 main characters and now she's writing a story with 3 main characters! There's more copycat things that I forgot. At first I was flattered but now I'm annoyed. I don't want to stop being her friend, because other than that she's a great friend, so what should I do?