From the New York City Public Library Collection; sepia tone removed by gogm. According to their notes, the print is after a portrait by John Bostock that I cannot locate.
Lady Williams-Bulkeley wears a lace pelerine over a dress with big imbecile sleeves making this early 1840s or 1830s. Her dress may also have a belt.
Keywords: British, hurluberlu coiffure, off shoulder vee neckline, floral bodice ornament, pelerine, lace, imbecile sleeves, belt, natural waistline, full skirt