Grace Kennedy, 20, was living a life typical of many young women - working, studying, spending time with loved ones, enjoying her hobbies - when one day she suddenly felt weak, something she assumed was just tiredness.

When the weakness and other issues like faintness and dizziness continued, the Mount Ousley resident visited her doctor, who told her it was likely vertigo and gave her exercises to do.

These didn't work and blood tests came back normal so Grace asked her doctor if there was anything more she could do and was sent for a MRI.

She discovered she had stage four medulloblastoma, a fast-growing brain tumour that most commonly occurs in young children but is rare among adults.

"It was about 2.5 weeks from the time that I started feeling sick to when I had the MRI and I got told I had a brain tumour," Grace said.

"So I've had to come to terms quite quickly with the fact that life will look very, very different for me and for my family."

That was a month ago and she has since had surgery to remove most of the tumour, but is now preparing for radiotherapy and chemotherapy, a treatment regimen that will run until at least June 2024.

And because of the damage chemotherapy can wreak on the body, Grace is also looking at fertility preservation measures so that she might have children one day.

She is travelling back and forth to Sydney for appointments but this weekend she and her mum Tracy will move into an apartment, thanks to the Sony Foundation, for the duration of her radiotherapy.

But Grace said she was putting her trust in her "very talented" doctors and knew she had friends and family supporting her all the way.

As well as the physical and emotional toll, the diagnosis also brings a financial cost for Grace and her family.

She has had to give up work (and put her studies for a Certificate IV in Travel and Tourism on hold) and there are expenses like petrol, parking and medical aids like a wheelchair to consider.

Ian said there were also medical costs they had to pay because there were no Medicare codes to cover the tests and procedures, due to the rarity of the paediatric cancer occurring in an adult patient.

"One of the things that was a big cost was, for my tumour, they have to do extensive testing to figure out its genetic markers, which then determines how much radiation it needs and how susceptible it will be to treatment... and that testing would be free if I was under 18 because it's a paediatric tumour, but because I'm 20, it costs $1000 to get that testing done," Grace said.

One of Ian's old school friends, Rita Finlay-Joseph, has launched an online fundraiser to help Grace and her family bear the financial impost.

Rita said she and Ian were part of a group of old school friends still in contact and when they heard about Grace, they wanted to do something to help.

"She's truly the most beautiful, kindest human being," she said, adding that Grace was only worried about how her illness was affecting others.

As of Monday evening, the fundraiser has attracted over $5000.

Grace thanked Rita and everyone who had contributed.

"I'm so very grateful for everyone that's left even just a kind message or sent through their thoughts and prayers... I'm just so thankful for everyone that's donated," she said.

Ian told the Mercury that the doctors said Grace should be proud for picking up on the fact something was wrong, because others often left it until it was too late.

"Go to a doctor, go get it checked out, and if you feel that something is wrong... continue to ask for more help or for a second opinion, because if I'd just taken it as vertigo... if I hadn't pushed for [the MRI] who knows what that would have then led to," Grace said.

The fundraiser for Grace can be found at www.gofundme.com/f/su9x4-please-help-our-grace-fight-brain-cancer.