A Victorian woman's sentence for killing a father-of-three has been slammed.

A Melbourne judge has granted mercy to a woman showing “deep and profound remorse” after she drove into and killed a man being sick on the side of a freeway.

Tara Brennan, who sobbed throughout her sentencing in the County Court on Monday, may spend just three-and-a-half years in jail after causing the death of 31-year-old Alan Dunlop on the Western Ring Road on May 7, 2016.

But the victim’s mother says people like Brennan are “getting away with murder”.

“She’s not remorseful. We’ve not even had an apology from them, not one,” Karen Dunlop told reporters outside court.

“It’s just not right. It’s got to change.”

Dunlop's friend Tim Archer agreed the sentence was insufficient.

"I think today's sentence just highlights the inequality and how the judicial system in Australia is not effective," he told reporters.

Archer added Brennan's remorse shouldn't contribute to sentence leniency.

"The tears today I don't think are for Al. I think they're self-pity tears - the fact this girl has now lost her freedom through her own choice."

Brennan previously pleaded guilty to culpable driving causing death and possessing a drug of dependence after 0.2g of methylamphetamine was found in her bag on the day of the crash.

A doctor previously opined Brennan was affected enough by ice that she would have been incapable of having control over her vehicle.

On the day of the crash, Alan Dunlop and his cousin were driving to Epping to fix a friend's window.

On the way, they pulled over in the emergency lane of the freeway so Dunlop could be sick, when Brennan crashed into their car at 83 kilometres per hour and trapped the victim under her vehicle.

The father-of-three died at the scene.

"This had tragic consequences for his family and friends, especially his mother and children," Judge Duncan Allen said to Brennan during sentencing.

"He won't be present to share their joy...or assist in the difficult times."

Brennan had been diagnosed with borderline personality disorder, post-traumatic stress disorder, social dysfunction and anxiety and depression.

Judge Allen described the case as "very serious offending with tragic consequences" but one with compelling and mitigating circumstances.

He detailed Brennan's history of mental illness and drug addiction following a young adulthood of abuse, "torment", depressive illness and suicidal ideation.

Judge Allen said he needed to deter "others from driving like maniacs on the road, like you did".

But he added, "the depth of your genuine and true remorse and contrition is so powerful", adding Brennan would not receive adequate psychiatric care in jail and her condition would deteriorate.

"Rehabilitation will not be aided by a sentence which you will find crushing," he said.

"The remorse in this case has been palpable. It's been evident even this morning as you've sobbed in the dock.

"There is no doubt in my mind that you suffer the most deep remorse and shame and guilt, having caused the death of this young man."

Brennan was jailed for six-and-a-half years, with a non-parole period of three-and-a-half years.

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