Sarah Ferguson was first discovered since the death of her former mother-in-law, Queen Elizabeth II, last week.
The Duchess of York, along with her ex-husband Prince Andrew, watched the florist tribute left for the late Queen on the exterior of Windsor Castle on Friday.
Affectionately known as Fergie, she praised her late ex-mother-in-law on Twitter earlier this week.
"I am heartbroken by the passing away of Her Majesty the Queen. She has left an extraordinary legacy: the best examples of responsibility, service and steadfastness, and a stable presence as our head of state for more than 70 years," she wrote.
"She selflessly dedicated her life to the people of the UK and the Commonwealth," she continued. "To me, she is the most incredible mother-in-law and friend. I will always be grateful for the generosity she showed me and maintained an intimate relationship with me even after my divorce.
"I will miss her, not what words can express," the Duchess concluded sadly.
Ferguson, 62, married the Queen's second son in 1986, and they have two daughters, Princess Beatrice, 34, and Princess Eugenie, 32. The couple announced their breakup in a scandal in 1992 when she was photographed to toe-sucked by American businessman John Bryan, whom he called her "financial adviser."
The couple formally divorced in 1996.
Despite their divorce, the couple remained very close and even lived in the same house.
She is also a staunch defender of her predecessor, who was forced to resign from the royal family after a disastrous BBC interview in 2019. Ferguson described her husband as "a kind, great man" and said her wedding was the happiest day of her life because "I married the best man in the world."
The Duchess reportedly grew closer to the Queen after the death of Prince Philip, who was known for hating his former daughter-in-law.
Currently, she and her ex-husband have taken in the four dogs left behind by the Queen.