Lady Mary was Walpole's half-sister by Maria Skerrett, who later became Sir Robert Walpole's second wife. In 1746 Lady Mary married Colonel Charles Churchill. Walpole praised her musical talents, and the music book she is holding may be the copy of Pergolesi's opera, L'Olimpiade that Walpole asked Mann to obtain for her in Italy. This portrait hung in the Great Parlour at Strawberry Hill.