Her article in thepeerage is here.
Upgrade image posted 5 April 2015 from ehdu.livejournal.com/631189.html.
Lady Barbara's bodice is concealed by her possible fichu, but the knotted waist band and loose skirt suggests Directoire period.
Keywords: Hoppner, Barbara Ashley-Cooper, Barbara Ponsonby, Lady de Mauley of Canford, Ashely-Cooper family, Ponsonby family, British, curly coiffure, fichu, vee neckline, bodice, sweetheart neckline, waist band, bows, close skirt, wrap