MARILOU, like her parents, is a fighter.

Jessica knew something was wrong when her then eight-month-old daughter’s left side went limp.

But it took five months of fighting and countless appointments until a regional clinic finally scanned her daughter’s brain. It triggered a whirlwind change of pace.

The family that fought for so long to be heard found themselves rushed to the Royal Children’s Hospital that day. It was little Marilou’s turn to be brave.

She had a brain tumour and underwent emergency 12-hour surgery – the first of several operations – followed by chemotherapy.

Marilou, 1, hasn’t had more than a week at home with her family, including Isla, 3, and dad Travis, since that September night.

“It’s this constant rollercoaster of ups and downs,” her mum said. “Every good thing comes with a bad thing and we rarely get good news.”

They were told it was a benign tumour … but in the wrong place. Then the treatment failed – twice.

Her mum said Marilou’s benign tumour didn’t behave like a “good” tumour and during chemotherapy – intended to treat the parts that had been too risky to surgically remove – it started to rapidly grow back.

Isla was too young to understand why her sister was ill, so they called the tumour Terry and told her Terry lived in Marilou’s head.

Before long everyone, including the treatment team, had adopted the name, inspiring the family’s new slogan: “Screw you, Terry”.

After several operations, Terry has, in part, finally got the message.

Marilou’s neurosurgeon, Patrick Lo, said the progress Marilou had made since her operation last week – when he made the difficult decision to perform “more aggressive surgery” than usual – was “absolutely fantastic”.

“I was facing a really massive dilemma here,” he said.

“If I don’t do anything, Marilou is going to die. But if I do something, and take a lot, I could really hurt her.

“In neurosurgery it’s always doom and gloom in the darkest hours.

“When you come out the other side, when there’s a light, it’s just the best feeling.

“This is what we live for.”

Marilou’s fight isn’t over.

Her mum said they had a “15 to 20 year battle” ahead where they will need to monitor the tumour – while investigating trial drugs – and operate again if it flares up, but she’s hopeful.

“Knowing that our neurosurgeon has taken a huge amount out this time, we know we’ve got time,” she said.

“I feel like there’s been a few times where I’ve almost crumbled, but the nurses have been there to make me stand on my own two feet and keep me going.”

For now her mum holds on to the little things, from Marilou’s progress in physical therapy to the nurses who stop by to play peek-a-boo, and her unwavering belief that she will one day watch her “two little girls go down the slide together”.

“It might be a couple of years from now, but there’s going to be a day where I’ll watch her play on a playground with her sister.”

And, with the team at the Royal Children’s Hospital behind her, dreams really can come true.