An Auckland woman described by prosecutors as having a history of revenge plots has been sentenced to eight years and three months' prison, five years after a bungled arson attempt resulted in the death of her intellectually disabled friend.

Jurors in the High Court at Auckland found the 32-year-old, who continues to have name suppression, guilty of manslaughter and arson in July.

"You are clearly not remorseful at all," Justice Geoffrey Venning told the defendant today as he ordered the eight years and three months sentence for manslaughter and a concurrent five-year sentence for arson. "You have not taken any responsibility for your offending."

Stephen Rhys Ewart's lifeless, charred body was found in the foetal position on the morning of December 9, 2017, outside a Mt Roskill flat where the defendant and her mother were in the process of being evicted. Sixteen milk bottles filled with petrol had been placed underneath the home.

Ewart, a 58-year-old described as having the mental capacity of a 12- to 13-year-old, had accidentally lit himself on fire in the process of committing arson for the defendant, Crown prosecutor David Johnstone told jurors during the trial.

While there was no physical evidence or CCTV footage placing the defendant at the scene, she had used Ewart just a year earlier to lodge a false assault allegation against a man who had helped her father divorce her mother, Johnstone alleged. And in 2008, she is suspected of having lit her then-boyfriend's car on fire as the relationship became acrimonious, he noted.

Stephen Ewart died in December 2017 after accidentally setting himself alight. Photo / Supplied

"It does give you an insight into what [her] tendencies were," Johnstone said, describing the defendant as already knowing through experience "just how coachable, just how susceptible Mr Ewart was".

"The fire in 2017 was far more likely to have been inspired by [the defendant] rather than Mr Ewart," he said.

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During today's sentencing hearing, Johnstone acknowledged the case is "unique" enough that there aren't a lot of previous cases to base sentences on. But he asked Justice Venning to take account of two things: "the calculated and methodical way in which the offending was put together in the week prior to the fire" and "the extent to which Mr Ewart ... was exploited".

Defence lawyer Tiffany Cooper noted that although intellectually disabled, Ewart "was able to make some decisions", which led to him being able to live independently and being known for having a "strong personality".

"He was someone who was still able to form a view as to whether or not he wanted to partake in the offending on the day he died," she said.

Cooper noted her client had a post-traumatic stress disorder diagnosis after having moved to New Zealand at 11 years old and being raised in "a dysfunctional and unstable family environment" that included domestic violence by her father. It resulted in a lonely life for her, which might have been what made her and Ewart so close, she said.

"They were both people without a great deal of social support," she said.

Venning told the defendant he accepts that she did not mean for her friend to die that morning, but she "cynically took advantage of his reliance" on their friendship, he said.

"While the case against you was a circumstantial one, it was an overwhelming circumstantial case," he said.

He agreed with the Crown that the woman's "calculated plan to exact revenge" was an aggravating feature of her offending. He also noted the danger to others besides Ewart. While the home he was trying to torch was empty, other families were alseep in adjoining homes, he said.

He allowed a four-month discount for her "cooperative approach" to the trial, agreeing to watch proceedings via audio-visual link after she tested positive for Covid-19 rather than insisting the trial be adjourned.