Sarah Mamalai says the National Disability Insurance Scheme gives her the chance to be a normal mum.
But after changes were made to the scheme last year, Ms Mamalai will soon have to pay for transport out of her own pocket.
"I don't understand why this change has happened," she told reporters in Canberra on Wednesday.
"It was perfect, for me anyway."
Ms Mamalai, who has had three brain surgeries as a result of cancer, already travels regularly for doctors appointments.
Soon, a simple trip from Canberra to Sydney for medical treatment will become unaffordable.
Ms Mamalai says this could jeopardise her volunteering with the Australian Brain Cancer mission as she will struggle to attend meetings.
Covering the travel costs herself is not an option because she does not work.
Ms Mamalai is calling on NDIS Minister Stuart Robert to reverse changes that barred participants from using their support plans to pay for transport costs.
Before the changes were made, users had core plans to pay for their care and a separate budget for transport.
Now, people cannot use their core budgets to pay for travel once they exceed their travel budgets.
Bill Aldcroft, a business manager for Quest Care, said one of the support provider's high-needs clients relied on their mother for transport.
Despite the person having an NDIS plan worth more than $500,000 a bureaucrat had noted: "Transport paid by mum."
Mr Aldcroft said Quest Care tried to invoice the National Disability Insurance Agency, which runs the NDIS, but was told the organisation was acting outside its remit by invoicing travel costs.
"They've made it quite clear that we are transgressing whatever legislation and that this is, I won't say fraud, but certainly this is something that's frowned upon," Mr Aldcroft said.
"We should have the right to choose, from the money you've given us, how we use it."
Labor frontbencher Bill Shorten says reversing the change is as simple as unticking a box.
Mr Shorten pointed to a recent review of the NDIS, which criticised the scheme's lack of flexibility.
"Parts of the NDIS are in danger of imminent collapse," he told reporters.
The minister said the national disability scheme was uncapped and demand driven.
"Claims of the government deliberately directing the NDIA to cut NDIS plans are false and are unnecessarily trying to create fear for participants," Mr Robert said through a spokesman.
Australian Associated Press