Diamond Marshall, the little girl who stole hearts back in 2011 when she hugged Kate Middleton during her royal visit to Canada, has passed away. She was 9.

A palace spokesperson has told CTV News the Duke and Duchess of Cambridge were saddened to learn the news.

Diamond Marshall was diagnosed with adrenal cancer at the age of five, just a few years after her mother, Memory, had died of another form of cancer at the age of 32.

Marshall overcame three separate struggles with cancer, but her family learned in November that she had osteosarcoma, a bone tumour common in children with cancer, and was going to die.

"We are incredibly saddened, yet relieved that Diamond is no longer suffering," her family said in a statement Tuesday.

"In her fight against cancer, Diamond was a warrior but she carried herself with the grace and dignity of a princess."

While being treated in hospital in 2011, she became fascinated with Prince William and Kate while watching their wedding from her hospital bed. She told The Children's Wish Foundation that her dream was to one day meet a princess.

On July 7, 2011, the foundation helped make that dream come true.

When Prince William and Kate emerged from their helicopter after touching down in Calgary, Marshall, dressed in a pink dress and matching band around her bald head, rushed over to the smiling Duchess. She thrust a handmade gift at her and then ran back to the safety of her father and stepmother.

Middleton urged the little girl to come back and after they exchanged a few words, Marshall threw her arms around Middleton for a hug.

Diamond's dad Lyall Marshall told CTV News later that year that the experience of meeting the royals had a lingering effect on his little girl.

"I think that it helped in her emotional healing," he said.

Marshall underwent several surgeries and rounds of chemotherapy in the first year after her diagnosis. Her cancer went into remission long enough for her to undergo a bone marrow transplant.

But in early November, doctors discovered Marshall's cancer had returned, this time as osteosarcoma, and the family was told the cancer was incurable. 

On Tuesday, it was announced that Diamond Marshall had succumbed to her illness.

A statement on the Hockey Marathon for the Kids Facebook page reads: "Very sad news today. Diamond Marshall, the inspiration for the original Hockey Marathon, has passed away.

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

Marshall's family plans to commemorate her life with a charitable initiative.