My flatmate copies me!

My flatmate has started copying me and it's really irritating.

I came home from work last week to find she was wearing my clothes, had used my make-up and had even borrowed a handbag.

For the last four months she has also been copying phrases I use and going to places that I go. She is just getting in my space way too much. I am not good on confrontation. How can I approach the situation?