A good biographical article can be seen here. A genealogical sketch is here.
From smallbay.ru/artrussia/lampi_iogann.html. Also posted to the Reign of Louis XVI - 1775 to 1789 Album here.
Urszula is dressed up to the latest French fashion with her curly bouffant coiffure with hair ribbon, fichu-like scarf, and full skirt. She may be wearing a sheath.
Keywords: 1789, Lampi, Urszula Dembińska, Dembiński family, Morsztyn family, Countess, curly bouffant coiffure, jeweled ribbon headdress, scarf, vee neckline, long tight sleeves, cuffs, full skirt