"Maria Amélie of Spain, wife of Charles III", Louis de Silvestre, circa 1700-1750
So-called portrait of maria amalia of saxony (1724-1760), wife of charles vii of naples, but it's probably a portrait of maria vittoria of savoy (1690-1766)
identification proposed by user ecummenic (talk) based on the comparison with a portrait of this princess located in the palazzo madama (see image below). Object Type: painting. Date: circa 1700-1750. Dimensions: height: 77 cm (30.3 in); width: 63.5 cm (25 in). Medium: oil on canvas. Collection: Unidentified location. Attribué à Louis de Silvestre - Marie-Amélie d’Espagne, épouse de Charles III