The sitter was probably Elizabeth Conyngham's daughter. Her article in thepeerage is here.
A young Lady maria smiles at the viewer wearing a very simple Empire dress adorned only with a waist band.
Keywords: 1824, Lawrence - Thomas, British, Conyngham family, Somerville family, Baroness, British, curly coiffure, square neckline, quarter length full sleeves, waist band, Empire waistline, close skirt, necklace