Tayah had just turned 12 when she was diagnosed with acute myeloid leukemia (AML), a rare form of cancer in which the bone marrow makes a large number of abnormal blood cells.

What was thought to be a case of "rare gingivitis" culminated in a frantic flight to Sydney just three weeks ago.

Mr Sidney said he was shocked to learn his little girl, who loves painting, the colour purple and Pretty Little Liars, would need to start chemotherapy immediately.

"I bawled my eyes out. I lost it," Mr Sidney said. "She's had a cold a couple of times, probably had a couple of days off school and that's about it you know, then bam, it hits you. It's pretty crazy."

Just 50 children are diagnosed with AML in Australia each year, and most cases are in males.

Mr Sidney said the chances of Tayah being diagnosed with this kind of cancer were incredibly slim.

"They said Tayah's leukaemia is only 0.8 per cent of cancers diagnosed," he said.

"She's always been so healthy. It's so sudden."

In the intervening weeks, the dad and daughter have had to learn a whole new vocabulary full of words most adults can't spell, let alone a 12-year-old child.

Their days are a rigmarole of tests and treatment but Mr Sidney said his daughter constantly amazes him.

"She's very courageous. She's just a trooper," he said. "The other night, she was pretty sick, she was throwing up all of the time and I'd just pass her the bag and she would just throw up, seriously heave it up and then go back to a conversation we're having or playing Uno."

In the upheaval of Tayah's diagnosis, the single dad has been forced to take extended leave from his job as it is unclear when the pair will be able to return to Canberra.

"I might not even be able to work this year, to be honest, so I've got to look in the long run of things and try and get help somehow. I'm just trying to keep my house I guess," he said.

Their family and friends and have managed to raise more than $11,000 in a little over a week to help the pair.

Tayah's school – St Anthony's Primary School in Wanniassa – even held a Purple Day in her honour.

Mr Sidney said it's hard to know what the future holds, but as Tayah is fast-tracked on to her second round of chemotherapy, he is quietly hopeful.

"Everyone up here is really supportive and positive and we're all positive, too. You've just got to roll with the punches," he said.

You can help the Sidney family by donating via their GoFundMe page: www.gofundme.com/2b7bpj7h