Fergie was formerly married to Prince Andrew, brother to King Charles.
So let’s take a look at Fergie’s complicated history with royal celebrations.
Has she received an invitation?

So what has happened in the past that has left her on this uncertain ground?
As a result, the late Prince Philip banned her from Christmas celebrations at Sandringham (via Cosmopolitan).
When King Charles took the throne in late 2022, he reversed that decision and invited her back.

Diana and Fergie had been close friends since their teenage years, and were in fact fourth cousins.
Because of this lifelong closeness, the two became natural confidantes when they also became sisters-in-law.
