Diamond Marshall, the little girl with a rare form of cancer who got her wish to hug the Duchess of Cambridge while the popular royal was visiting Calgary in 2011, has died.

Diamond was six years old when she caught the world's attention during Kate Middleton and Prince William’s visit to Calgary.

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Diamond Marshall, who was six when she greeted the Duchess of Cambridge with flowers and a hug in 2011, has died. (Canadian Press)

The girl had wanted to meet a princess after watching the royal couple’s wedding from her hospital bed, a dream that was made possible by the Children's Wish Foundation.

Kate is a duchess, not a princess, but the distinction was unimportant to Diamond, who gave the royal couple a bouquet of flowers, a homemade gift and two hugs. 

A spokesperson from Buckingham Palace says the royal couple was saddened to learn of her death.

'Her story inspired so many'

Diamond had a rare but aggressive form of cancer. It had been in remission, but recently returned.

"[She] had survived cancer three times previously, but in early November we discovered she had osteosarcoma and we were told this would be the last chapter of her journey," said her family in a statement.

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Diamond Marshall laughs as her father Lyall Marshall, right, hugs her after playing hockey for 246 hours with 39 others to set a Guinness World Record for the longest hockey game ever played in May 2012. (Jeff McIntosh/Canadian Press)

They say Diamond died peacefully on Monday evening. While there is a lot of sadness, her family says they are relieved she is no longer suffering.

"We are incredibly thankful for the time we had with Diamond and we will cherish the memories we made with her," said the statement. 

"In her fight against cancer, Diamond was a warrior but she carried herself with the grace and dignity of a princess. She touched many people along the way and her story inspired so many."

Her family plans to set up a charitable initiative in the girl's memory in the near future.

Diamond was the inspiration behind an 11-day hockey game to raise money for the Alberta Children's Hospital Foundation, among other causes. 

The Hockey Marathon for the Kids Facebook page posted a message about the girl on Tuesday.

"During her short life, her courage was an inspiration to many," said the post. "We'll miss you Diamond."