1759 Augusta of Saxe-Gotha as Dowager Princess of Wales by Allan Ramsay (location unknown to gogm)
From Wikimedia; spots removed from background with Photoshop by gogm.
This portrait of Princess Augusta shows her wearing a dress adorned with a lace cape that flare out in back, bertha, and a set of engageantes. The shadows make it difficult to resolve if she is wearing a robe à la française or anglaise. The shape of her neckline is also not readily identifiable - I believe it is a square neckline. She does wear a wide skirt.
Keywords: 1759, Ramsay, Augusta of Saxe-Gotha, Princess, Wettin family, Welf family, British, straight coiffure, cap, square neckline, bertha, lace, cape, three quarter length close sleeves, engageantes, vee neckline, panniers, ruching, neck band, floral bodice ornament, bracelets