A final post-mortem examination by forensic pathologist John Rutherford concluded that it was accepted methamphetamine was capable of raising blood pressure and therefore precipitating a brain haemorrhage.
Given the high levels of methamphetamine in Ms McMillan's blood it was probable that this occurred in this case, Dr Rutherford concluded.
A police investigation found no records of Ms McMillan having any involvement with illicit drugs.
"The inquiries also established that Ms McMillan appeared to be a happy, healthy, young woman who was well admired and respected,'' the findings said.
She had a successful career working at AXA New Zealand and had a reputation of being very hard-working and dedicated.
Her fiance of 16 years worked in Tauranga and returned home each fortnight, and everything appeared to be normal in their relationship.
She had a very close and loving extended family and there appeared to be no obvious stresses in her life, Coroner Smith said.
Her health was good, but in the period before her death her partner and brother both indicated she had been taking an excessive amount of Panadol.
Her immediate family and friends were not aware she took any form of drugs and police had not been able to find the source of the methamphetamine she had taken.
Coroner Smith concluded his report stating Ms McMillan had died of an intracerebral haemorrhage in the context of methamphetamine toxicity.
