In the two years since her diagnosis, Annabelle Potts became the focus of fundraising efforts as her parents hoped against hope that the doctors who said their daughter had no chance of recovery were wrong.

Annabelle was rushed to Sydney Children's Hospital on December 30, 2016, undergoing treatment for a rare brainstem tumour called diffuse intrinsic pontine glioma (DIPG).

The family's plight became a very public cause that inspired great generosity. As money was raised, Annabelle's parents, Kathie and Adam, sought help at a Mexican clinic that offered treatment not available in Australia.

For a time, her parents said the treatment seemed to have stopped the growth of the tumour.

Now, though, the death of Annabelle has been announced.

A Facebook posting by her grief-stricken mother, Kathie Potts, on the Love for Annabelle page said: "This morning our hearts were shattered to pieces when we lost our darling Annabelle. She left us quickly and peacefully.

"I won’t say you gained your angel wings, as you already had them on earth. Everyone who’s life you touched know how generous and selfless you are. There are no adequate words to describe your beautiful heart. I am so incredibly privileged to have been your mother.

"You’re suffering has ended and ours has begun, a burden we will carry to know you are at peace, watching over us."

Last year Mrs Potts described their struggle. "We're focused on achieving small milestones. The first is, we got her to preschool. The next is for her to learn how to read. She just loves learning,"  she said.

It was far beyond what doctors told her and her husband when Annabelle was diagnosed with what has now turned out to be an incurable illness.

"They said, 'There's no treatment. Even with radiation, she has six to nine months to live. Go home and make memories'," Mrs Potts said.

Mr and Mrs Potts decided not to take the advice.

They decided, instead, to take her to the clinic in Mexico where she received a combination of treatments not available in Australia because they were deemed to be experimental.

Mrs Potts argued for the treatment despite opposition.

At one stage the federal Health Minister, Greg Hunt, in a letter to Mrs Potts, sided with the Australian medical community in maintaining the treatment in Mexico had not demonstrated its efficacy.

Mr Hunt said the advice put to him was that any stabilisation or improvement in Annabelle's health was due to radiation she received in Australia.

Despite the medical advice, the defiant hope of Annabelle's parents inspired great generosity from the people of Canberra. The numerous sessions in the Mexican clinic at $30,000 a time were way beyond the budget of a public servant and a carpenter but the city put its hands in its pockets and financed the trips and treatment.

There were individual acts of kindness like that of Lalangi Abhayapala, Annabelle's teacher at Miles Franklin preschool in Evatt, who shaved off her long hair to raise money.

A seven-year-old at Jerrabomberra Public School organised a "Wear it Yellow for Annabelle – School Challenge" where people were asked to wear yellow and donate money, yellow being, according to the organiser, the "colour of sunshine, hope and happiness."

And there were collective acts of kindness like a "Love for Annabelle" fundraising dinner.

Mr and Mrs Potts expressed their gratitude for all the immense effort. "We are just so grateful to the Canberra community because we could not do this without them," Mrs Potts said last year.

Since the announcement of the death, there has been an outpouring of grief, with hundreds of postings of condolence on the family's Facebook page.

One reads: "My heart is broken for you and your gorgeous family. Annabelle is one of the bravest little fighters with the warmest heart and biggest smile. I feel so lucky to have met your beautiful princess."