Her article in thepeerage is here.
From a Google search; enlarged by half. Also posted to the Reign of Louis XVI - 1775 to 1789 Album here.
This is British Casual for 1783 with a simple dress and hoodless Brunswick-like coat.
Keywords: 1783, Romney, Frances Carpenter, Frances Gough, Lady Calthorpe, Carpenter family, Gough-Calthorpe family, Baroness, British, high bouffant coiffure, ribbon headdress, criss-cross bodice, waist sash, fur-trimmed coat, quarter length flared over-sleeves, close under-sleeves