Born Lady Mary Hervey on 31 October 1725, she was successively daughter, sister and aunt to Earls of Bristol, and also aunt to the 2nd Earl of Liverpool (prime minister 1812-1827). Her marriage to George Fitzgerald was an unhappy one, ending in a separation. About 1765 she rejected the life of high society, devoting herself to the spiritual life and her wealth to charitable work. She was a close friend of John Wesley and one of John Fletcher's correspondents (see Arminian Magazine, 1796). She died on 9 April 1815 after her clothing had caught fire, and was buried in the forecourt of Wesley's Chapel, London.
'I could not but admire her humility, condescension, and Christian love. She seems to prefer every one to herself, and, if permitted, would become, like her Lord and Master, the servant of all. Her conversation is very spiritual and edifying, and her simple, humble, free and open behaviour, cannot but cause her to be beloved at the same time as it makes her a blessing wherever she comes.'
Joseph Benson, quoted in James Macdonald, Memoirs of the Rev. Joseph Benson (1822) p.287