The De Landre-Line family stayed up until 1am, laughing and playing Lotteria - a form of bingo the Potts' family had become addicted to during stays in Mexico where five year-old Annabelle - one of Ellie De Landre-Line's best friends - was having experimental treatment for her rare brain cancer.

The next morning, the De Landre Line's received a devastating phone call. Annabelle had died at Sydney's Bear Cottage.

The friendship between Annabelle Potts, 5, and Ellie De Landre-Line, 7, was short but fierce.

The little girls met at Annabelle's Lemon Face Challenge at Parliament House in November and were virtually inseparable from then on.

Ellie wrote poems for Annabelle, drew her pictures, and even wrote and illustrated a book about how the princesses in heaven had selected Annabelle to come and join them. Ellie also penned a letter to prime minister Scott Morrison asking for a meeting and demanding funding for her dying friend.

But the highlight of Annabelle's final days were the videos Ellie made and texted in an attempt to make her younger friend laugh. In one video, Ellie used pretzels as bunny teeth, in another, a banana as a Pinocchio nose.

"Sometimes I'd send her 10 videos a day," Ellie laughed.

"Annabelle was super sweet, super kind, caring, sharing and she was very tough trying to battle with cancer."

Ellie is now convinced Annabelle is in heaven, surrounded by her favourite colours - pink and purple - with her own herd of unicorns and probably wearing a dress like Belle from Beauty and the Beast.

"I think heaven's a really great place for her because she can do whatever she wants whenever she wants," Ellie said.

"She can have so much fun with everybody else there - heaven is a great place."

Ellie's mum Jo described the girls' bond as "wonderful" and said Ellie had been a source of joy for Annabelle during her illness.

"[Annabelle's mum] Kathie said Annabelle got so much help from Ellie because Ellie was a normality in their life and just pure joy," Jo said.

"A lot of the time for Annabelle it was very much about the sickness and Ellie would walk in and she's got a very big personality and big voice and a big heart to match."

The day Annabelle died, Ellie said she received "a signal" from Annabelle that everything was okay.

"We went to drop off some pictures that I drew for Kathie and Adam then all of a sudden a butterfly came out of nowhere," she said.

"And it flew around the bag and then she flew around a bowl of lemons. It felt like the butterfly was signalling us, like Annabelle was signalling to us."

A poem by Ellie De Landre-Line (with a bit of help from her mum, Jo)

I have this friend called Annabelle
She's so little, she's only five,
But she's so sick with brain cancer
She's in a battle to survive.

I have this friend called Annabelle
Living her sweet life day by day,
A girl so young and cute
But she's too sick to run and play.

I have this friend called Annabelle
The cancer she has is so rare,
There's so little funding to help
I have to say it's so unfair.

I have this friend called Annabelle
She's fought this battle for a while,
The cancer is trying to win
Now it's stolen her gorgeous smile.

I have this friend called Annabelle
She has family close by her side,
They fight so bravely for a cure
We need you to stop and decide.

I have this friend called Annabelle
Research grants could cure her one day,
She needs a medical breakthrough
To help, there's no other way.

I have this friend called Annabelle
It's hard for her family to cope,
Knowing that a cure could be found
Please help them and give them some hope.

I have this friend called Annabelle
She is loving and sweet and pure,
Medical research could help her
I'm pleading, please help find a cure.