My friend is copying me at everything?

there's this girl and she literally is copying me at everything. she is basically trying to be me. she had no friends so I became friends with her and ever since then she is trying to hang out with all my other friends all the time without me, and whenever I buy something she does too. she switched classes to be in more of mine and she is stealing my friends pretty much. and I told her I like north face jackets, and she bought one. I have black uggs and true religion jeans from my birthday (which was a month before christmas) and she got the same ones for christmas. and don't say that I should be honored that she wants to be like me because I am not. it's getting out of hand, she is stealing my friends, and it's really annoying. what do i do?! thanks in advance