Her daughter
Georgiana had been married to the Duke of Devonshire for about a year when
Gainsborough portrayed her here in 1775. But I believe it is more likely that
daughter Georgiana was running around the house when this was painted in 1765.
Georgiana Poyntz' dress in this Gainsborough is a good example of 1765 dress; there may be a typo in the usual Internet date of ca. 1775.
Keywords: 1765, Gainsborough, Georgiana Poyntz, Poyntz family, Spencer family, Countess, British, straight coiffure, square decolletage, bows, modesty piece, lace, elbow length tight sleeves, engageantes, robe à la francaise, neck ruff