It claimed in court today that when Milner most probably crushed up to 50 tablets of anti-histamine Phenergan into her husband's food, she laid the killer blow with a pillow over his face.
She then faked suicide notes, it is alleged, and even sent a text message from his phone or her own phone suggesting he had committed suicide.
The text read: "I'm sorry honey I can't keep going on like this. I love you so much and tell Ben I love him."
Milner was unhappy in her marriage and was motivated to murder her husband by the prospect of a $250,000 life insurance payout, which had a non-suicide clause expire just weeks earlier, said Crown prosecutor Kathy Basire.
When Mr Nisbet was found dead in bed in May 2009, police originally ruled he had taken his own life.
However after a coroner raised doubts over the death, and when a second police probe was launched Milner became a major suspect.
Workmates, friends and family all told police that Milner had talked about killing her husband, the best way to do it, and even offering $20,000 in cash to one of her sons, to "get rid of him".
Two years after Mr Nisbet's death, she was arrested and charged with murder.
The Crown says a new boyfriend, Barry Hayton, moved into the family home within weeks of the death.
Emails read out in court today showed how Milner was "obsessed with money" and how she was going out to dinner and movies with her new "sugar daddy" by the next month.
"Who said being a widow is all that?" she would tell a friend.
In talking to friends and workmates, Milner would berate Mr Nisbet and even talked about how she could "get rid" of him in a car accident.
"I thought it was quite a strange conversation to have and tell other people about it," said Lynette Marie Maynard, who worked with Milner at GSL, a Christchurch-based grounds maintenance firm.
Mrs Maynard said Milner was "a little bit obsessed" with money and would bemoan the fact that she couldn't afford holidays.
The court heard that in email correspondence with another friend, Chantelle Janine Allen, Milner said Mr Nisbet had just returned safe and sound from a work trip: "Bugger," she wrote.
On June 10, 2009, just over a month after Mr Nisbet died, Milner emailed to say she was sick of workmates pussy-footing around her at work because she thought she was coping well.
"It's a lot easier to get over things when you marry an A-hole," she said.
She also claimed that her son Adam Kearns was "telling everyone that will listen that I killed Phil," and that he wanted $20,000 in hush money.
The Crown said she tried to kill Mr Nisbet twice on April 15, 2009 by giving him Phenergan, which put him in hospital.
But the Crown said Milner completed her task on May 4 by giving him another overdose, before putting a pillow over his face.
She then staged the scene to look like a suicide, the Crown said.
The trial, before Justice David Gendall, continues.
