Ms Morris' bashed, naked body was found in the back of an abandoned car near Christchurch International Airport on January 6, 2012.
A senior officer involved in the Milner homicide investigation - launched more than two years after police originally ruled Mr Nisbet's death a suicide - told APNZ that there was no link between to the two murders.
"There is absolutely no connection between the two cases," he said.
Mr Nisbet's sister, Lee-Anne Cartier, who has been praised by police for her sleuth work in bringing Milner to justice, never knew that Milner had been in a relationship with someone else who would go on to kill.
"It just shows what sort of person she is, and how she was attracted to someone else as evil as her," she said.
Ms Cartier said she had often wondered who 'Keith' was.
When it emerged that officers said Milner had asked them to phone Keith after she had phoned 111, she just thought it was a mistake.
"I had no idea who Keith was. I thought the officers had written the wrong name down and instead meant Barry [Hayton]."
Mr Hayton, who moved in with Milner weeks after Mr Nisbet's death, said during the trial that he is still Milner's boyfriend.
Under cross-examination, he told the jury that he knew Milner's friend Keith, and had met him previously.
Bonner had been in a sexual relationship with Ms Morris which ended in 1995, but they stayed friends.
On January 3, she went to his house for dinner.
He attacked her from behind, bashed her head, before strangling her with her own leggings.
Bonner then dragged his friend's body through the lounge, out the back door and into her car.
He dumped the car at Greys Rd, near the airport, with the victim semi-naked and face-up. The vehicle and body were found by a passing jogger three days later.
The next day he handed himself in to Papanui police Station reading about the matter in the newspaper.
Milner will be sentenced on February 20.
