Get a disguise and come in while she's home. Tell her to strip and piss on her head and then leave. Tell her you don't know who it was as you never hand your key out and then change the locks.
Last time I think I had a roommate I was like 25 as my best friend and myself dumped our girlfriends within a month of each other so had a bachelor pad for a bit which was a pretty good time filled with random girls/parties. Had a girl from Venezuela stay with me last year for like 2 1/2 months which was cool but that's probably the most I could handle few months here or there as I'm pretty clean for a guy and too old now to deal with people annoying me or fucking with my shit. If I'm dropping a dong in it my tolerance level goes up but if just a roommate too much headache for a few extra bucks.
