She won't stop copying me..! help?

Ok it seems like you have a big copy cat on your hands which is annoying as i have experienced. What you need to realise first is that this girl really looks up to you so much so she wants to be you. She needs to find her own and the only way to help her and yourself is separation. If you value her friendship sit her down and tell her how you feel if not stop hanging around her and if she ask why tell her the truth. Simple as