It comes after Sarah Ferguson - who is grandmother to Eugenie's son August- revealed that the Queen is "doing well".
She said: "She is doing well. She is my icon. When I see her, I pinch myself to remind myself how lucky I am. She is an extraordinary woman."
The queen - whose husband Prince Philip died earlier this year aged 99 - carried out an in-person engagement with General Sir Nick Carter, the chief of the defence staff at Windsor Castle on Wednesday, her first since October 19.
And earlier this week, her eldest son, 73-year-old Prince Charles, insisted his mother was feeling "alright", while carrying out an engagement during his and wife Camilla, Duchess of Cornwall's tour of Jordan.
He said: "She's alright thank you very much. Once you get to 95 it's not quite as easy as it used to be. It's bad enough at 73."