Is this supposed to be Naples? According to Madame Guillotine, "On the run from the French Revolution, the celebrated society portrait painter Madame Vigée-Lebrun went on a tour of some of the royal courts of Europe, where she painted portraits and recorded her impressions of her noble and royal sitters for a gleeful and very appreciative posterity. One of her first stops was the court of Marie Antoinette’s elder and favourite sister, Maria Carolina, Queen on Naples at the Palace of Caserta…" So that is Vesuvio smoking in the lower right.
From thevictorianlady.tumblr.com/post/7322744924/princess-sapiena-nee-potocka-or-dancing-with.
Pelagia's pose is theatric, but her dress probably is not in this 1794 Vigée-Lebrun portrait.
Keywords: 1794, Vigée-Lebrun, Pelagia Potocka, Potocki family, Sapieha family, Countess, long curly coiffure, head band, chemise, quarter length full sleeves, bodice, waist band, natural high neckline, close skirt, arm bands, wrap