I called a friend who has been hosting house parties for years. I asked him all these same questions. He gave me some advice that doesn't really illuminate what went wrong, but it sure seems to the point.
He said "I wouldn't worry about it too much. Almost always when a couple has a jelousy meltdown like that, you never see them at parties again. Since you'll probably never hear from them again, it doesn't really matter much what their problem was."
