I want to make my girlfriend's room mate feel uncomfortable. Is this going to be a problem?
Um, what? For real? Why do you want to treat her so coldly?
She is a bitch, we've had issues before and she never even apologized to me
It's not okay to try to make people's lives more difficult or to try to make them uncomfortable. Your girlfriend's roommate might not even realize that she has upset you in the past, and she might be willing to make amends if you tell her what the problem is.
She's a cunt, she needs to pay for it.
You are not God and can't be someone who needs to be in charge of other's feelings and moods regardless of how you and them have been poorly matched together. You should just walk away and spend time making new friends.