She married Edward Herbert, Viscount Clive on 9 February 1818.[2] He succeeded to the Powis earldom in 1839, at which point Lucy became Countess of Powis. The couple had seven children:
Lady Lucy Caroline Herbert (c.1819–1884), who married Frederick Calvert and had no children
Lady Charlotte Elizabeth Herbert (1821–1906), who married Hugh Montgomery and had children
Lt.-Gen. Rt. Hon. Sir Percy Egerton Herbert (1822–1876), who married Lady Mary Caroline Louisa Thomas Petty-FitzMaurice and had children
Very Rev. Hon. George Herbert (1825–1894), Dean of Hereford, who married Elizabeth Beatrice Sykes and had children
Hon. Robert Charles Herbert (1827–1902), who married Anna Maria Cludde and had children
Maj.-Gen. William Henry Herbert (1834–1909), who married Sybella Augusta Milbank and had children.
The Earl of Powis died on 17 January 1848 at his home in Powis Castle after being accidentally shot during a pheasant hunt by one of his sons, the Hon. Robert Charles Herbert, ten days earlier.[3] He was buried at St Mary's Parish Church, Welshpool. The countess herself died in 1875 at Walcot, Shropshire, where the family had another home.
A portrait of the countess, at around the time of her marriage, was painted by Frederick Richard Say and is held at Powis Castle.[4]