I went through the name Cholmondeley in thepeerage and I believe, but cannot prove, this Hester Cholmondeley, née Edwardes, with an extra e in the spelling.
From Wikimedia.
Mrs. Cholmondeley is dressed for warmth and wears a full, but probably unsupported, skirt in this 1791 Hoppner portrait.
Keywords: 1781, Hoppner, Cholmondeley family, British, curly coiffure, ribbon headdress, scoop neckline, scarf, wrap, fur, long tight sleeves, full skirt, gloves