The invitation, however, is a break in royal protocol, with many royal fans noting that the Middleton family has never been extended an invitation to the festivities.
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.
The Queen's invitation would show respect and also acknowledge that Meghan, unlike Kate, has no other family in Britain, the source said.
Doria gained worldwide praise following her daughter's wedding, for her "dignity."