She is not yet listed in thepeerage. An old version of Burke's Peerage on the Internet showed she married one Henry Brouncker of Boveridge, but does not even list a maiden name or when she lived.
From www.artrenewal.org.
Lady Hariet wears an old-style fichu and one of the new-fangled muslin Directoire-style dresses with a plunging vee neckline - filled in by a chemise.
Keywords: Hoppner, Hariet Brouncker, Harriet Brouncker, bouffant coiffure, ribbon headdress, trapezoidal neckline, fichu, chemise, over-dress, natural high waistline, belt, gloves, wrap