The Sydney grandmother, who also spent much of her life advocating for women of the Australian Army, died on Monday after a short battle with illness.

"She was a truly special lady who will be greatly missed by so many," her family posted to Instagram on Tuesday.

"The simple act of stopping Daphne in the street and holding her hand meant more to Daphne than anyone could ever imagine."

She made international headlines, including the front page of the UK's Daily Mirror, when she met Harry and Meghan outside the Sydney Opera House during the Invictus Games in October.

Dunne spoke at length with the expectant parents and patted Harry's face affectionately as she congratulated the couple on their exciting news.

"I wished them well with the baby on the way and said this is what Harry has been waiting for for so long," she told AAP at the time.

"I got a cuddle too."

That, and two other meetings in 2015 and 2017, left a mark on the Duke of Sussex who made sure he sent her a 99th birthday message last week.

Dunne first came to prominence in 1945, when her first husband Lieutenant Albert Chowne was posthumously awarded a Victoria Cross for bravery in New Guinea in the Second World War.

The medal itself was presented to Dunne by Queen Elizabeth II's uncle, Prince Henry.

Dunne, herself a corporal in the Australian Women's Army Service during the Second World War, later married again - to former Changi prisoner of war John Patrick Dunne.

As recently as November, the war widow was donning replicas of her husband's medals and rubbing shoulders with NSW Governor David Hurley to attend the launch of defence force book "The Victoria Cross: Australia Remembers".

Australian Associated Press