Her husband, Henry Percy, 6th Earl of Northumberland, had wished to marry Anne Boleyn instead of her.
In January 1524, Lady Mary was forced to marry Henry Percy, heir to the earldom of Northumberland, who had fallen deeply in love with Anne Boleyn, then a lady-in-waiting to Queen Catherine of Aragon.
[2] Henry succeeded his father as the 6th Earl on 19 May 1527, and Mary was henceforth styled as the Countess of Northumberland.
In June 1532, Mary sought an annulment, on the grounds that her husband had a pre-contract with Anne Boleyn.
In later life, though she had a grant of abbey lands from the Dissolution of the Monasteries, she was suspected of being a Roman Catholic, a favourer of Mary, Queen of Scots, and of hearing mass in her house.