Kerry Lee Sunderland will spend at least one year and nine months behind bars after a horrific crash that killed a 14-year-old boy and her partner on July 11, 2020.

The 39-year-old from Menah - about seven kilometres from Mudgee - was sentenced in Dubbo District Court on Thursday after pleading guilty to two counts of dangerous driving occasioning death and two counts of dangerous driving occasioning grievous bodily harm.

Sunderland, who was 37-years-old at the time and on her green p-plates, was driving her Mitsubishi sedan on the Castlereagh Highway between Dunedoo and Mendooran when the fatal crash occurred

According to an agreed statement of facts tendered in court, Sunderland and four others were in the car, along with two unrestrained animals - a cat moving throughout the vehicle, and a dog which was sitting on the front passenger's lap.

It was about 3.20pm, when Sutherland rounded a left-hand sweeping bend, but failed to negotiate it properly in the wet conditions.

The mother lost control of the vehicle when it crossed into the opposite lane. Instead of correcting the vehicle she simply took her hands off the steering wheel.

The vehicle left the road and crashed into a tree.

At the time, the Westpac Rescue Helicopter Service reported all five occupants were trapped in the wreckage and had to be cut free from the vehicle.

Sadly a 14-year-old boy who was seated in the passenger's seat, and her 25-year-old partner seated behind her suffered fatal injuries and died at the scene.

A 17-year-old girl suffered serious leg fractures and was airlifted to John Hunter Hospital in Newcastle for surgery.

A 13-year-old buy suffered a bi-lateral femur fracture and required a blood transfusion so was airlifted to Westmead Children's Hospital.

Sunderland escaped with a fractured arm and dislocated shoulder.

Following inquiries, crash investigators attended Westmead Hospital where they arrested Sunderland in the foyer. Upon her arrest police also found a rolled 'joint' containing 0.3grams of cannabis in her handbag.

In an electronic interview with police, Sunderland admitted she was a regular user of cannabis and had consumed some prior to the crash. She also said she had very little sleep in the days prior to the incident.

A further sample of her blood taken at the hospital after the crash revealed she had less than a milligram of amphetamine and methylamphetamine in her system.

Despite drugs being detected in her system after the incident, the Crown said it was at a level they could not prove contributed to impairing her driving ability.

Following the crash the vehicle was examined and found to have no mechanical defects that would have contributed to the loss of control.

Police found a number of factors contributed to the fatal crash on July 11, 2020.

These included Sunderland's sleep-deprived state, a distracting environment within the vehicle, the way she negotiated the bend in the road conditions at the time and her response to the loss of control and failed attempt at correcting the vehicle by removing her hands from the wheel.

In the Dubbo District Court on Thursday, Judge Craig Smith made a finding of special circumstances due to it being Sunderland's first time in custody.

He found the mother will require a significant extended period on parole to assist with rehabilitation and reintegration into the community.

Sunderland was sentenced to a term of imprisonment of three years and six months, with a non-parole period of one year and nine months behind bars. She will be eligible for release in November 2023.