To the woman whose BF calls her by his female friend's name: One of the most common signs of being in love with someone is having "mentionitis" - ie: you keep bringing up their name, involuntarily, because you're thinking about them CONSTANTLY. It's a classic symptom of infatuation. If my fiance started called me by someone else's name, I would be seriously concerned. If it happened more than a couple times, we would be having a serious conversation about this other person. If it ever happens during sex, I would say that's the end of the relationship.