Sarah Ferguson heaped praises on Queen Elizabeth saying she has been her 'greatest mentor.'
Appearing on Monday's episode of the Tea with Twiggy podcast, Fergie called the monarch the "person who believes in me."
"I think to myself that honestly, my mother-in-law has been more of a mother to me than my mother," she said.
Fergie's mom Susan Barrantes left the family when she was a child to move to Argentina with a new husband, professional polo player Héctor Barrantes. She died in a car crash in 1998.
The Duchess added, "I absolutely admire the incredible way Her Majesty is so modern ... and how flexible, and how understanding, and how forgiving and how generous."
Earlier, when talking about her ex-husband Prince Andrew, Fergie said, "Whatever challenges he has, I will stand firm to the co-parenters we are together. I believe he's a kind, good man, and he's been a fabulous father to the girls."