This is probably Susannah, the seventh of eight children of John Poulett, 1st Earl Poulett. His article in thepeerage does not get to Susannah in the listing of his children.
Lady Susannah's bodice has a center tab, a feature seen repeatedly 100 years earlier. Her lace collar resembles the broad collars seen in the 1630s. Her lace collar also resembles 1630s collars. Her sleeves and engageantes are also flashbacks.
Keywords: 1730, Seeman - Enoch the Younger, Susannah Poulett, Poulett family, British, straight coiffure, scarf, bows, collar, lace, scoop neckline, three quarter length puffed sleeves, forward-back flared engageantes, jacket bodice, girdle, vee neckline, full skirt, theatrical dress