Need advice on getting along/resolving an issue with boyfriend's prissy roommate...?

One of my boyfriend's two female roommates is being an absolute b***chy snob to both him and I everytime I come over. His other roommate who is also a female is also getting tired of this roommates behaviour and they have been friends/roommates for years. My boyfriend has also been friends with both of them for years, and only recently moved in with them. I was wondering if there was anything I should be doing to resolve this issue since neither my boyfriend or the nice roommate have strong enough backbone to do anything about it. My boyfriend keeps saying that he'll do something about it "next time", but still has yet to do anything about it and I'm just about at my wits ends with both her and the situation in genaral, especially because coming over has become awkward and has put a damper on spending time with my boyfriend. Some advice please???