But unlike other children, Harriett's dream only has a 50 per cent chance of happening.

She was diagnosed with cystic fibrosis at just four weeks old. Two weeks earlier, doctors told her parents she had Prader-Willi syndrome, a lifelong genetic disorder affecting appetite, growth, metabolism, cognitive function and behaviour.

"We had just got our head around what PWS would mean for our daughter's future when we were ushered into a room with multiple specialists and geneticists to be told she also had cystic fibrosis," Harriett's mum, Melissa Pryor said.

To be diagnosed with both cystic fibrosis and Prader-Willi syndrome is rare. In Australia, one in 2500 babies is born with cystic fibrosis. The survival rate for Australian children with cystic fibrosis is 50 per cent, and those who survive have an average life expectancy of just 38.

"That day we received a handful of scripts for various medications that were, and still are, required to be given daily so she can stay as healthy as possible," Ms Pryor said.

"It took us many, many weeks to get our new routine into place.

"Not only did we have a tiny newborn to look after, but we also needed to give her medications around the clock."

On average, one in 25 people carries the cystic fibrosis gene, most of whom live symptom-free and are completely unaware they are carriers. However, they can pass the gene on to their children.

"There was no family history but as we discovered, we were both carriers of the cystic fibrosis gene," Melissa said.

Two carrier parents have a 25 per cent chance of having a child with cystic fibrosis each pregnancy.

There is no cure for the disease.

Harriett's aunt, Anna Pryor, started a display of Christmas lights to not only raise money for research but to let families have a break from the stress of everyday life.

"We used to do Christmas lights before but not as big," Anna said. "When Harriett was born we had a purpose to up our game and help where we can through our lights.

"As a family, we love looking and driving around to see fairy lights and you get a good feeling – all your worries wash away and you just get to watch all the pretty lights."

Anna and her husband, Dave, have displayed the lights at their Gordon home and raised money for for five years.

"If we can help a worthy cause such as Cystic Fibrosis ACT, why wouldn't we? They help so many people who genuinely need the help," she said.

"All donations made are put into the Everyday Hero account, which are funds raised to replace essential medical equipment that are used heavily throughout the life of a person with cystic fibrosis."

In 2015, Anna and Dave raised just over $2600. Anna said they had been planning this year's light display since June and next year's will raise money for Prader-Willi syndrome.

Harriett's mum Melissa said she was grateful to her brother and sister-in-law for donating their time and funds to the light display.

"At this year's preview I had to fight myself to maintain composure," she said.

"I often get teary thinking about Harriett's future and to see Anna, Dave and their children actively involved in helping create a better future for Harriett is such a lovely way of supporting Harriett and our family."

Melissa said even with her diagnosis, Harriett is a very social and outgoing girl. She said now that Harriett is older, she is able to remember what medications are required when.

"She loves butterflies and reading and has had an excellent year at kindergarten," Melissa said.

"She has surprised us with how resilient she is and how she takes every new challenge in her stride."

Cystic Fibrosis ACT president Tania Minogue said the organisation relies on the generosity of local donors and fund-raisers to be able to provide vital equipment and support.

"Without the ongoing enthusiasm of people like Anna and David and events like the Fingleton Christmas lights, we would struggle to support those who are living with cystic fibrosis and need our help in the ACT and surrounding region."

The lights are on display at Fingleton Crescent, Gordon. You can donate here.

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