She was the daughter of Sir Henry Hobart, 4th Baronet, a Norfolk landowner who was killed in a duel when Henrietta was aged eight. Her mother Elizabeth (nee Maynard) died a few years later.
In 1714, they travelled to Hanover, hoping to ingratiate themselves with the future George I of Great Britain. Henrietta met and became mistress to his son, the future George II, and was appointed a Woman of the Bedchamber to his wife, Caroline of Ansbach. In 1723, the prince made a financial settlement with her husband in exchange for her services as royal mistress.
She and her husband officially separated, and after Charles Howard's death in 1733, Henrietta re-married, in 1735, the Hon. George Berkeley, son of the Earl of Berkeley.
After leaving the position of mistress to George II, Henrietta purchased land on the banks of the river Thames, having received a very large financial settlement from him. Marble Hill House in Twickenham was built for her on this site by the architect Roger Morris, who collaborated in its design with the Earl of Pembroke, one of the 'architect earls'. When her second husband died, in 1746, she retired there permanently. Her many friends included Charles Mordaunt, 3rd Earl of Peterborough, and Alexander Pope wrote of her, in his poem "On a certain lady at court":
