I have two roommates. I get along well with the guy - we just flirt a lot and make sarcastic comments to each other. Sometimes we take walks together or go to the store. I also get along great with the girl - she is super sweet, we have lots to talk about and she might come to a concert with me this weekend.
Unfortunately, the guy seems not to have gotten over the girl's "surprise" arrival last week (it wasn't her fault the landlord didn't notify us of the new tenant) and he is being a jackass to her. She walked into the kitchen today and said "hi" to him, and he ignored her and walked into his room. Unless I'm in the room, he doesn't talk to her, and then kind of only through me. She asked me if I knew why he didn't like her, and my only thoughts were that he holds ridiculous grudges, or that she's super attractive and he's trying to resist the urge to jump her. This doesn't directly impact me but it makes things very unpleasant for her and she is counting down the weeks till he moves out. I can't decide if I should casually ask him if he is still annoyed at her being here, or what.