Hijacking comment to repeat my advice from an earlier thread:   Write up a roommate agreement yesterday.  Here's a good template of one.  They're not really legally enforceable, but they DO set down terms in writing, and can be used as a club.      DOCUMENT EVERYTHING! If you both agree on anything, you have a document with both your signatures on it agreeing to it. If there's a mess in the sink, you've got pictures of it. The moment she starts getting dramatic again (because it will happen), you're recording it. Make all requests over a written medium, like email or text, and keep screenshots on a thumb drive, or cloud storage. With a previous roommate, when bill time came around, I would send an actual physical bill to the apartment via registered mail, and demand a signature from them.   Lock your shit DOWN. Get a fridge locker. Seriously, this eatbeast strikes me as the type to get petty revenge by adulterating food. Mark your non-fridge food so it's harder to be tampered with. Does your room lock? If it does, start, and if it doesn't, get a lock. Lock your computer, and basically make your shit as Fort Knox as possible.   Make sure people around you know what's going on, including any authority figures. Don't just vent to us on the 'tubes, we can't really do shit besides offer advice and sympathy. I'd even go so far as to stop by the local police station and letting them know that while nothing has happened YET you've got concerns over your flatmates mental health, that way there's something on file in case shit goes sour.