The woman was diagnosed with breast cancer 11 years ago, and underwent treatment through her health insurance.
The cancer recently returned under her arms, and she is going through the public system for treatment.
"I think it's wrong to say to people that if you go private you're going to get better treatment, because I don't think that's always the case.
"I've been private for the last 10 years and have had check ups privately, and it still didn't stop cancer from coming back."
She said insurance companies saying people would receive better healthcare if they took out insurance put extra pressure on sufferers who were already under enormous stress.
But she said if insurance companies truly did allow access to better treatments, they should bring down their prices to make it more affordable for everyone.
Mr Carter said his company offered lump sums of money if people needed to pay for a drug that was not subsidised by Pharmac, or found themselves away from their job for a long period of time while they were recuperating.
"For certain types of cancer, those drug treatments can be really expensive."
He denied his company was scaring cancer patients into taking out insurance for the latest treatments.
"It's just a fact, unfortunately one in three (will develop some form of cancer in their lifetime)."
Auckland Hospital clinician and insurance advisor Rob Young said public healthcare gave a "very good healthcare service".
"New Zealand's Pharmac-funded healthcare system does not always offer patients the most advanced drugs available. Some expensive treatments which are commonplace in other first world countries, for example, are not available to the average New Zealander."
One type of drug not available here was zytiga, for advanced prostate cancer, which reportedly worked well for patients, Dr Young said.
Breast Cancer Aotearoa Coalition chairwoman Libby Burgess said Dr Young had a point.
"His view is shared by quite a few medical practitioners who are frustrated at the lack of funding for innovative medicines by Pharmac. They keep a very tight cap on the medicines' budget and the things they will fund for patients in New Zealand."
But she said New Zealand did have excellent public healthcare.
Dr Burgess would not comment on whether health insurers should lower their prices, because prices would vary with each company.
Pharmac said it would not comment on the issue.