This should be Marquise Beatrix-Stephanie-Renart de Fuchsamberg d'Amblimont. A brief genealogical chart for her is found here. The de Laage family is apparently Belgian.
Photo - René Gabriel Ojéda; image size increased by half and image sharpened by gogm.
Carrogis' style is about the same, but the dress, probably a sheath, is different from the dresses of his late 1760s sitters. She wears a short riding coat with cape top, its tails, sleeves, and cape decorated with ruffled trim.
Keywords: 1783, Carrogis, Marquise, French, high curly coiffure, headdress, vee neckline, fichu, jacket, ruffles, long close sleeves, cuffs, waist band, panniers, flounces, maxi-length skirt, shoes