Lady Dorothy Sidney, later Countess of Leicester, née Percy (c. 1598-1659) was the eldest daughter of Henry Percy, 9th Earl of Northumberland, and his wife, Lady Dorothy Devereux. In 1615, she married Robert Sidney (1595-1677), later 2nd Earl of Leicester, by whom she had children.
The uncertainty over the identification of the sitter stems from the existence of an identical miniature by Isaac Oliver described as a portrait of a lady called Arabella Stuart, now in the Rijksmuseum, Amsterdam (see exhibition catalogues Nicholas Hilliard & Isaac Oliver, London, Victoria and Albert Museum, 1971, no. 171 and A Gentle Kind of Painting, Edinburgh, The Scottish Arts Gallery, 1975, no. 67).
The sprig of rosemary the sitter holds is a symbol of remembrance, love, fidelity and loyalty.