This is her Wikipedia article, "Elizabeth Grey, Countess of Kent (née Lady Elizabeth Talbot) (1582 – 7 December 1651) was the wife of Henry Grey, 8th Earl of Kent. She was a daughter of Gilbert Talbot, 7th Earl of Shrewsbury and Mary Cavendish. She married Grey on 16 November 1601, at St Martin's-in-the-Fields. They had no children, and the Earl died in 1639. Afterwards she is thought to have married the writer, John Selden, who had worked for the Earl. After her death, her collection of medical recipes was published as A Choice Manual, or Rare Secrets in Physick and Chirurgery Collected and Practised by the Right Honourable the Countess of Kent, late deceased. It was an interest she shared with her younger sister, Alethea Howard, Countess of Arundel."
From bbc.co; lightess added to bring out bodice and sleeve details.