Last week, Sonya McMaster, pleaded guilty to dangerous driving occasioning death while under the influence of drugs and alcohol in Dubbo Local Court.

The 33-year-old's case has been committed to the Dubbo District Court for a sentence hearing in September.

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In court documents, police said McMaster had a blood alcohol reading of 0.090 and tetrahydrocannabinol (THC) present in her system, when the silver Holden Barina she was driving left the Tomingley West Road, about 60 kilometres southwest of Dubbo.

The car rolled multiple times before it landed on its roof in the early hours of December 28 last year.

A 34-year-old passenger, Peak Hill woman Shani Hando, was thrown from the car during the crash and died at the scene.

McMaster was treated by paramedics before she was taken to Dubbo Hospital for treatment and mandatory testing.

Police initially charged McMaster with dangerous driving occasioning death, and negligent driving occasioning death.

They later added three additional charges, which were withdrawn or downgraded when she pleaded guilty to dangerous driving causing death, drive under the influence.

Three back-up charges will coincide with the charge McMaster pleaded guilty to, they include driving with tetrahydrocannabinol (THC) present in oral fluid, negligent driving occasioning death and mid-range drink driving.

These back-up offences will be taken into consideration by the District Court Judge, secondary to the main offence McMaster pleaded guilty to.

McMaster remains out on bail until the matter returns to the Dubbo District Court on September 17.