I could not find anything about her in thepeerage. There is a genealogical sketch of her here.
From Philip Mould; left, top, and right edges fixed with Photoshop.
Elizabeth Jackson's dress keeps up with the dresses worn by French Ladies in their portraits. A rural landscape is the sole nod to casual style.
Keywords: 1760, Gainsborough, Elizabetha Margaretta Richards, Richards family, Morton Pleydell family, British, straight coiffure, hair jewelry, capelet, vee neckline, bodice, square décolletage, long close sleeves, engageantes, spoon waistline, full skirt, choker necklace, earrings, robe à la française