If a girl calls you "B" in a text or conversation, she is almost certainly using a popular modern slang abbreviation that typically means "bro," "bae," or "bestie." Depending on the dynamic of your relationship and the tone of the chat, "B" can range from an affectionate pet name used by a romantic interest to a casual, platonic term used among close friends to address you comfortably. It signals a relaxed, friendly communication style where formal boundaries are dropped entirely in favor of casual peer slang.