A woman sends a message to a man. What does she mean by calling herself a concubine?

Isn't this meaning obvious enough? If it's a footman, it's your wife's, and he also addresses you as emperor. Maybe she is an optimistic, cheerful and humorous girl. Getting along with her should be a happy thing. If he just delivers, the footman can't do it. In this case, it is a terrier, which has nothing to do with whether he likes you or not. I don't know if it was sent later.