This is her brief Wikipedia article, "Elizabeth Percy, Countess of Northumberland (1646 - 19 September 1690) was a British courtier. She was one of the Windsor Beauties, painted by Sir Peter Lely.
Her father was Thomas Wriothesley, 4th Earl of Southampton, and mother was Lady Elizabeth Leigh. She married Joceline Percy, 11th Earl of Northumberland, on 23 December 1662: they had two children:
Lady Elizabeth (1667–1722).
Henry Percy, Lord Percy (1668–1669)
She traveled with her husband to Italy, where he was taken ill and died in Turin, the next year. Upon his death, being a wealthe heiress, she married Ralph Montagu, 1st Duke of Montagu, at Titchfield, Hampshire, on 24 August 1673; they had two children:
John Montagu, 2nd Duke of Montagu (c. 1690 – 5 July 1749).
Anne Montagu, married Alexander Popham.
Elizabeth was an important patron of the artist Peter Lely, who painted her several times. Her portraits were among the Windsor Beauties at Hampton Court and among the series of beautiful women portraits, ordered by Cosimo III de' Medici, Grand Duke of Tuscany."