ARGH HOW can i stop her copying me!!!?

I have this friend who copies me soo much its really annoying. I dont think anyone can appreciate how annoying it is. Im not up myself at first i thought 'its in my head!!' but then it got ridiculous. I cant stand it she has the same outfits as i do, same haircut, says the same things shes even dying her hair 2 b the same as mine. Dooont say its flattering. argh im so streesssssssed. What do i do? Ive brought it up with her once before and she was like well sorry ... shes even started flirting with my ex blatantlyyy!! I changed my style too she followed. What the eff do i dooo?