Wakefield is the daughter of Katherine Mary Alice (née Baring) and Sir Humphry Wakefield, of Chillingham Castle in Northumberland. She has two brothers; Captain Maximilian Wakefield (born 1967), an entrepreneur and racing car driver, and Jack Wakefield (born 1977), former director of the Firtash Foundation and an art critic who writes for The Spectator and other publications. A third brother, William Wakefield, was born in 1975 and died in infancy.
In 2015, following an online petition, Wakefield was forced to apologise and amend an article she had written for The Spectator in which she described an 18-year-old who had recently died in a moped crash as a "thuggish white lad".
Her father's Chillingham Castle website refers to her as "Daughter Mary, a musician and painter, [who] is also Assistant Editor of The Spectator".
On 25 April, Wakefield wrote an article for The Spectator about her experience when both she and Cummings contracted COVID-19. On the same day, she was a guest on BBC Radio 4's Today programme, discussing the same event, as part of a series of recordings by survivors of the viral disease. On 22 May it was reported, following a joint investigation by The Daily Mirror and The Guardian, that Wakefield and Cummings had driven 264 miles (425 km) from London to Durham in late March to stay in a cottage at her father-in-law's farm, while both, reportedly, had COVID-19 symptoms, although Cummings states that his symptoms appeared the day after the journey was made.
An eyewitness saw Wakefield on 12 April walking in Barnard Castle in the company of Cummings and their son, after a complaint to the Durham Constabulary by another witness who claimed to have seen Cummings with a group of people in the same town. Following an investigation into these reports, Durham Constabulary stated that whereas the trip to Barnard Castle might have been a minor breach of the lockdown regulations, the trip to Durham itself was not. Durham Constabulary stated they would take no further action in the matter. Alleged inconsistencies between Cummings' account and his wife's have been discussed in the press, and reported to the Independent Press Standards Organisation, the magazine's regulator.