A young lady is a female child who has just done something dreadful.

Martin’s witticism (in her familiar “Miss Manners” vein) skewers how social labels can be used to manage reputations rather than describe reality. “Young lady” sounds like a respectful, even genteel category, yet the punchline suggests it is often deployed precisely when a girl has violated expectations—an admonishing euphemism meant to reassert decorum. The line highlights the gap between idealized femininity and actual behavior, and it satirizes the moralizing tone adults adopt when policing girls’ conduct. It also implies that “ladylike” status is treated as conditional and disciplinary: bestowed or withdrawn depending on compliance with social rules.