After hearing she could be out on parole by January 2022, the woman continued sobbing and thanking Judge Nicole Noman "so much" for the minimum penalty of one year in prison.

The then-47-year-old caused a five-vehicle pile-up after consuming cannabis and veering into oncoming traffic on the NSW mid north coast, on September 26, 2017.

A truck smashed into the rear of the car, killing her 72-year-old mother while her six-year-old daughter suffered extensive injuries and severe brain trauma, and requires lifelong care.

The woman was found guilty by a jury for dangerous driving occasioning death and dangerous driving occasioning actual bodily harm.

Before the crash, she and other family members were unwell from a "bad case of the flu," while visiting her parents who offered to help with the long drive home to Queensland from south of Sydney, according to the agreed facts.

Experts say she consumed cannabis somewhere along the journey and showed signs of fatigue at least 12 minutes before the collision.

Her erratic driving caught the attention of others as she swerved into other lanes. After finally veering onto gravel she over-corrected into oncoming traffic, colliding with another car.

Following her trial, she offered an explanation that she had been swerving to avoid potholes but this was dismissed by Judge Noman for a number of reasons.

"Both victims voluntarily entered the car undoubtedly with the expectation she would protect them," Judge Noman said.

The judge said she had failed to take full criminal responsibility as she continued denying ingesting the cannabis, while there had been ample signs she should have pulled over much earlier.

In a "big sorry letter" to the court, the offender had offered her deep remorse to family and the community for what she called the "horrific accident".

"It is not an accident," Judge Noman said.

Defence barrister Peter Williams in June submitted there were exceptional circumstances where the daughter needed the immediate care of her mother, and showed evidence of her declining health since she was taken into custody.

Although doctors initially thought the girl was brain dead, paralysed and facing almost certain death, in the three years since the incident she has recovered remarkably.

"She will live a diminished life with a reduced potential," Judge Noman said.

The judge noted many traumatic life experiences throughout the offender's life while her brother holds his sister accountable for their mother's death.

Cannabis has long been an issue for the woman but now with this "life-long reminder of her conduct," the judge was confident she would not drive again while under its influence.

Her previous criminal record showed a number of drug-related charges including couriering large amounts of cocaine, more than 10 speeding offences, and one for negligent driving.

The judge accepted the mother had dedicated her time before jail to looking after her daughter who genuinely wanted and needed her support at home, and would continue doing so.

She has been sentenced to a maximum term in prison of three years and three months. She is first eligible for parole on January 26.

"Thank you so much Your Honour," the woman repeated in between sobs.

Australian Associated Press