The answer is Lady Frances Anne Vane. Charles William Stewart, 3rd Marquess of Londonderry adopted the surname of Vane in 1822 so as to inherit her family estates in County Durham and elsewhere in 1822 on condition he would adopt the surname Vane after Londonderry.
Conquer and Challenge: Uncovering the Extraordinary Life of Charles Vane, 3rd Marquess of Londonderry