On 22 April 1799, Lady Elizabeth married
John Manners, 5th Duke of Rutland, who had succeeded to his father's dukedom in 1787 when he was still a child. He was the eldest son of
Charles Manners, 4th Duke of Rutland, by Lady Mary Isabella Somerset (a daughter of
Charles Somerset, 4th Duke of Beaufort). Together, they were the parents of ten children: • Lady Caroline Isabella Manners (1800–1804), who died young. • Lady Katherine Isabella Manners (1809–1848), who married
Frederick Hervey, 2nd Marquess of Bristol, and had seven children. A pencil portrait of her, by Henry Bone, after John Hoppner, is held by the
National Portrait Gallery.
Estate management The Duchess's interests included gardening and estate management. She took forward improvements begun by her father-in-law,
Charles Manners, 4th Duke of Rutland, but interrupted when he went bankrupt. She supervised landscaping works at
Belvoir Castle and included a model farm. A fire in 1816 almost destroyed the castle. The rebuilding was largely entrusted to the Duchess and cost around £82,000. The ''Gentleman's Magazine'' commented that "What many individuals would have required a century to execute, her perseverance in a few years achieved." and influenced the building of
York House on the Mall on behalf of
Prince Frederick, Duke of York and Albany, the brother of King
George IV, with whom she had an intimate relationship. ==Coat of arms==