My freshman year of college, I had a nightmare room mate. She had a massive makeup bag that took up half of our bathroom counter, and the rest of the counterspace was covered in her powder foundation and hair. She never cleaned it up, either. She wore so much perfume that you could smell it through the closed door of the bathroom.
She always had friends over, but flipped out and talked shit about my friends on the rare occasion that we spent some time in the room.
Because my college was 250 miles away from home, my partner was only able to come visit me at school 2 or 3 times during the entire year I was there. My room mate was always entertaining male guests, but complained extensively when MY partner was there, and even acted rudely toward him.
She knew that I used to be a self-harmer, so she made lots of jokes about how she wanted to cut over things like a test being difficult or her homework being confusing.
The final straw was when she flipped out over something completely ridiculous. I'd dyed my hair blue and pink the night before, and received a text in the middle of class from her, saying I'd left hair dye "ALL OVER" the shower and I needed to clean it up. I looked when I got back, and discovered that "all over" meant that there were 2 drops of blue dye on the shower floor. I sprayed it with 409 and they washed away easily. I knew she was PMSing, so I went and got her a pack of M&M's for when she returned. She came stomping in, tried to start an argument, realized she wasn't going to win, and then gave me the silent treatment. FOR THE REMAINING 2 MONTHS OF THE SEMESTER.