She was deaf and was married by signs, in 1753, to her first cousin, Murrough O'Brien, fifth Earl of Inchiquin, first Marquess of Thomond, and first Baron Thomond, of Taplow, in England, K.P.
She lived with her husband at his seat, Rostellan, near Cork Harbour.
She succeeded to the Earldom on 6 December 1756,[1] when her mother died without male issue.
By his Lordship, she had an only surviving daughter, Mary, the fourth Countess.
The Marquess of Thomond died in consequence of his horse falling with him in Grosvenor Square, on 10 February 1808, in his 85th year.