Yeah~ she might be mad but it's your computer and you have a right to revoke permission anytime you want. Besides, it sounds like you didn't give him permission to use it. It was immature if you allow him to play without permission but I thought you were going to say you cooked the pizza. That would have been wrong.

Hopefully you and your roommate can work things out ~ It's been a LONG time since I had these issues but I know it wasn't easy. Best of luck to ya.