This portrait has been attributed to Thomas Hudson who died in 1779. The Lady shown here, according to an article in thepeerage, married in 1777. But her coiffure and under-sleeves are in keeping with Hudson's heyday more than 1777. There was, according to thepeerage, a Bridget Heathcote, born 1n 1723, who married Earl of Morton John Douglas in 1755. I believe this is Lady Bridget Heathcote.