From Wikimedia; three spots in background removed with Photoshop by gogm.
Daria is not wearing anything like an 1814 dress with the off shoulder vee neckline and natura; waistline announced by a belt. This portrait looks like a Lawrence work. If it is, it was one of his later works.
Keywords: Princess Daria Lieven, von Benckendorff family, von Lieven family, Princess, mistress, Klemens Metternich, hurluberlu coiffure, knotted bun, ribbon headdress, off shoulder vee décolletage, upper puffed sleeves, waist band, natural waistline, earrings, wrap