Jessica Falkholt, 29, has died after a horrific Boxing Day crash that killed three members of her family.

A spokesperson for St George Hospital confirmed on behalf of Jessica's family that Falkholt died at 10.20am today.

"Jessica passed away from serious injuries sustained in a motor vehicle accident on December 26," the hospital said.

The Home and Away actress' life support was switched off on January 11 after several operations but she remained in a critical condition for days.

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She was pulled from the wreckage of the Boxing Day crash near Ulladulla with her sister Annabelle, 21, who died in hospital three days later. Their parents, Lars, 69, and Vivian, 61, died at the scene.

The driver of the 4WD that slammed into the family's car was also killed in the crash. Craig Whitall, 50, was a serial traffic offender and was reportedly travelling home from a Nowra methadone clinic when the crash happened.

The state government said there will be a thorough investigation into what caused the crash. NSW drivers are also expected to be subject to more roadside drug tests by 2020 with increased penalties for drug drivers.