For those taking notes, your girlfriend may respond negatively to going to bed alone while you have one-on-one time with her friend or roommate (or any other woman) late at night, especially if the other is being "nice."
But the typical response to a minor misunderstanding like that is to make the communication more explicit with a simple request that the boyfriend come to bed and share that you felt upset about it, trusting that your caring boyfriend will feel sorry, make a note and try to do better next time. Not to lead with accusations of ill intent and quickly escalate to a full range of emotional manipulation and threats of physical violence.