I had a roomate who used to disrespect my stuff. I dont think it was done maliciously, just more like she was oblivious to the fact that it bothered me. Stuff like borowing my clothes and not washing/returning them (i'd have to get them from her closet). Taking my quarters for laundry and replacing them with pennies, nickels and dimes. And other annoying stuff like taking my extra Venus razorblades, and using my MU w/out asking. The worst was when they had people sleep over in my bed when I was out of town for the weekend, and the people over threw up on my carpet, sheets, and in my hamper (empty at the time thank god). I was SOOOOOOO mad LOL.
I confronted her about it, and how it made me feel, and she was a lot better about it. I basically told her that if it continued I would move out. I went to homedepot the next day and bought a lock for my door, and had my boyfriend install it when the house was empty. It doesn't matter who your living with, they need to learn to respect personal space.
I'd get in her face about it. She's a terrible person if she doesn't apologise, and her mother should be ashamed for raising such a disrespectful person.