Is it wrong that I don't want my roommate's (nice) girlfriend around all the time?
What is wrong with her?
Let me explain the situation. He was supposed to bring his hot girlfriend over, but she had to cancel at the last minute.
I don't think it is fair to judge someone by how they look. You should discuss your concerns with your roommate to avoid problems.
What, it's not just about looks, she's boring, sloppy, and ugly out of dress. She sucks in bed, he always complains about the sex.
It's wrong to try to interfere with your roommate's relationship by not wanting his girlfriend to come over. It seems you should try to get to know her as a person and not just judge how she looks.