Annabelle Falkholt, the sister of former Home and Away star Jessica Falkholt, has died three days after a horror crash left her fighting for life in Sydney's Liverpool Hospital.

The 21-year-old was travelling in the back of her family's car with her sister Jessica when they were involved in a head-on crash near Sussex Inlet on the NSW south coast.

Annabelle was pulled from the wreckage with her 28-year-old sister after both cars went up in flames but sadly died in Liverpool Hospital's Intensive Care Unit this afternoon.

Australian star of the new Romper Stomper TV series Jacqueline McKenzie led the celebrity support for the sisters after the fiery crash that killed their parents.

It comes amid news the other driver involved, Craig Anthony Whitall, was known for previous traffic offences and drug use, according to the Daily Telegraph.

"Jess is a brilliant, kind, beautiful actress," McKenzie wrote online. "This is utterly devastating news."

Jessica Falkholt's co-star on Home and Away, James Stewart joined in to rally the acting community behind the performer, including a tribute from fellow co-star Pia Miller.

Jessica, 28, and Annabelle, 21, were left in a critical condition after the Boxing Day crash near Ulladulla.

The 28-year-old, a graduate from the National Institute of Dramatic Art who has played a role in Home and Away and other Australian television series, was travelling with her family when their vehicle was involved in a collision with a four-wheel drive.

Witnesses pulled the girls from the wreckage as the vehicles were engulfed in flames but her parents died at the scene, along with a 50-year-old man named as Craig Anthony Whitall.

Whitall was a serial traffic offender and known drug user, The Daily Telegraph reported. He had been jailed for driving while disqualified and was driving on P plates having only recently got his licence back, the newspaper said.

Whitall's son Shane paid an emotional tribute to his father on Facebook, saying: "This was around the same time you lost your life this morning".

"I love you with all my heart dad and will forever miss you you were my hero I don't give a f*** what anyone says you showed me alot in my life more than youl ever know its such a tragedy to loose you I LOVE YOU DAD RIP XXXXXOOOOO" (sic).

Jessica is in a critical condition in St George Hospital in the south of Sydney.

Co-star Jackson Heywood, writing on Instagram, called for people to drive safe alongside a photo of Ms Falkholt.

"Can we please send all our support, love and prayers to Jess and her sister Annabelle, fighting for their lives after their crash on boxing day," he said. "Much love darlin. Im with ya. May u both make a full recovery."

Network Seven said the Home and Away family are sending their love and support to the actress and her sister.

"Although her time on set was brief, once a part of the Home and Away family, always part of the family," a spokesman said.

The road toll in NSW is currently at 21 after a crash claimed a woman's life on Thursday morning.

She was driving a van that collided with a heavy vehicle travelling in the same direction on the Hume Highway at Gunning, police said.

- With AAP