Her article in thepeerage is here.
From the Bonham's Web site.
Lady Seymour is depicted in an 1820s dress that looks Napoléonic, but has a steep A-line skirt. Her neckline appears to be higher in the center in Renaissance style.
Keywords: Chalon, British, Mary Gordon, Mary Seymour, British, hurluberlu coiffure, crescent neckline, modesty piece, full cap sleeves, cuffs, ruffles, no waistline, A-line skirt, necklace, wrap