A Melbourne woman has been sentenced to five years' jail for the manslaughter of her abusive partner, who she killed in a "freakish accident" by causing a sign to split his head open.

Jessie Donker, 31, began driving towards Richard Powell in a carpark at Sunbury, north of Melbourne, after he attacked her as she slept inside her car in the early hours of January 8, 2017.

The court heard Mr Powell, 32, had pulled Donker out of the car by her hair before punching her in the face.

It heard she got back in the car and began driving at him in an attempt to taunt and frighten him, something she felt he had done to her over many years.

But Donker's car hit a parking sign, which bent and struck Mr Powell on the head, splitting his skull.

He was killed instantly.

Donker will be required to serve two years of her sentence before becoming eligible for parole.

Donker 'lost self control'

In sentencing, Supreme Court Justice Michael Croucher described the death as a "freakish accident" and accepted Donker had not meant to hit Mr Powell with the car.

He said it was completely unexpected and unforeseeable that the pole would bend at the precise angle required to hit Mr Powell, let alone strike his head and cleave it "like an axe".

The court heard Donker had lost custody of her children, was unemployed and often slept in her car in the period leading up to the accident.

Justice Croucher said she had "lost self-control" after being dragged out of her car by her hair in another instance of domestic violence she had suffered over a long period.

"She was in what she reasonably believed was a hopeless state with respect to her life circumstances, including the loss of her children, as a result, at least in part, of the behaviour of Mr Powell," he said.

"In my view, to be dragged by the hair from a car and assaulted yet again in those circumstances is likely to cause even the most resilient and even-tempered person to lose self-control and act out in a violent manner."

Jessie Donker suffered a long period of domestic violence at the hands of Richard Powell, the court found. ( Facebook: Jessie Donker )

Donker called triple-0 immediately after the accident and was arrested by police later that day. She pleaded guilty to manslaughter.

Victim's family says sentence not enough

Outside court, Mr Powell's mother, Antonia Powell, said she was very upset listening to the judge's sentencing remarks.

"It was only giving her side of the story," Mrs Powell said.

"Throughout their relationship, it has been violent, but she's also been an instigator.

"She could be out in January, it's just not enough.

"She could have driven away at any time, not keep going after him and after him," she said.

Mr Powell's father was too emotional to speak to the media.

Justice Croucher said Donker had good prospects of rehabilitation and accepted she was genuinely remorseful.

"Since Ms Donker's own children are victims of her crime, she will forever have a constant reminder of the hurt she has caused whenever she thinks of them being without their father," he said.

Ice use fuelled violence in relationship

The couple's relationship became abusive when Donker was pregnant with their first child, the court heard.

Mr Powell, who abused the drug ice, would physically, psychologically and verbally abuse Donker, including by grabbing her around the throat.

The court heard Donker would sometimes react violently by trying to assault Mr Powell.

Justice Croucher said police would sometimes be called.

"Usually, however, as many victims of domestic violence do, Ms Donker would devise a thin cover story for what had happened, or understate things, or decline to make a statement, or simply ask that her abuser not be charged," he said.

"After all, she still loved him. He was the father of two of her children. And she believed he loved her."

Donker's non-parole period means she will become eligible for release in eight months, taking into account the time she has already served.