"And they said 'no, you have to have a letter from your doctor'."
The nurse, who is originally from Hamilton but now lives in Bunbury, Western Australia, said she had never been asked for any medical certificates outlining her condition even when going through international airport checks.
She was shocked at the question.
"I said I didn't realise I was going to be asked for a letter from my doctor because I'm from Australia and I don't have one."
"They said 'no you can't come in'. I was kind of a bit rude about it, I said 'I can show you my scars if that's enough'."
Ms Wheeler said she was shocked and deeply hurt by the experience.
Exacerbating things was that some of the patrons in the casino were in "rather scraggy" attire.
"I was more tidily dressed than half of the people there and I tried to explain my situation but there was just no point of discussion."
In an emailed response to questions, a SkyCity spokesman said it had security and surveillance measures in place to ensure guests were identifiable while on site.
"We do not allow hats to be worn inside the casino as they obscure the identity and faces of customers," the spokesperson said.
"These are outlined in our dress code policy."
The spokesman said there were exceptions to this rule "that include medical and religious circumstances".
"If staff are not alerted to medical circumstances, they cannot make exceptions to these security measures. Due to privacy reasons we are unable to talk about specific details of this case."
Race Relations Commissioner Dame Susan Devoy urged the casino to "do the right thing" by being "reasonable and flexible when enforcing their dress code".
"Their customer was wearing a beanie because she is undergoing chemotherapy: she wasn't wearing gang colours - there's a big difference," she said.
