Doria was also invited to tea at Windsor when the planned wedding of Megan and Prince Harry. Last year she invited the then newly engaged actress to spend Christmas with the royals, breaking years of tradition that decreed only those who had married immediate members of the royal family could join them at the lunch table.
Following weeks of drama surrounding Meghan's father Thomas Markle and her extended and estranged family members in the US, Doria was praised for her composed and graceful appearance at the royal wedding.
A royal source said that the move was "a very thoughtful gesture", and quite unique to be honest.
The Duchess of Cambridge's family has joined the royals at church on Christmas morning but they have stayed at nearby Anmer Hall rather than Sandringham itself.More news: Elon Musk to Develop a 'Futuristic, Blade Runner Pickup Truck'
The invitation is believed to be a show of respect and also an acknowledgement that Markle has no other family in Britain.
Doria's calm, warm demeanour appears to have impressed the Palace, after she was seen chatting to her in-laws at the royal wedding.
She is known to be very close to Meghan, 37, and is said to even be planning a return to London to help with her new grandchild in the New Year.More news: Blizzard Says It 'Didn't Pull Any Announcements From BlizzCon'
The 74-year-old former lighting director has courted controversy over multiple interviews he has given over Meghan and the royals.
Mr Markle pulled out because of health problems just days before she was due to walk down the aisle and admitted he had staged paparazzi pictures.
Kensington Palace said "No comment" when asked by ET Canada.More news: Stephen A. Smith: Duke Basketball Can Go Undefeated