Jane Maxwell, Duchess of Gordon, c 1749 - 1812. Wife of the 4th Duke of Gordon (With her son, George Duncan, 1770 - 1836. Marquess of Huntly, later 5th Duke of Gordon. General). Note: the Duchess is wearing the “chemise à la reine” dress.
(Source: nationalgalleries.org)#chemise a la reine #George Romney