Babysitter charged over tragic crash that killed policeman's daughter.

A babysitter who was behind the wheel for a horrific smash the that saw her four-year-old passenger die has been charged with dangerous driving occasioning death.

Courteney Matthews, 18, was driving with three young girls in the car when they collided with another car on the Bruxner Highway in the small New South Wales town of Casino.

Matthews had  four-year-old Elle Underhill and her two-year-old sister Elaina in the backseat and a seven-year-old in the front seat.

Matthews’ red Mazda 323 was ripped apart in its collision with a Subaru Liberty.

The 18-year-old escaped with minor injuries but Elle was killed and Elaina was flown to Lady Cilento Children's Hospital, in Brisbane, with serious injuries.

The unnamed seven-year-old was treated in hospital for shock and the 81-year-old driver of the other car was hospitalised with an injured sternum.

The tragedy of the story only grew as the local policeman called to the scene was also the father of the two youngest girls.

Steve Underhill was unaware his daughters were involved until he arrived at the scene.

Witness Tazman Currie told The Daily Telegraph that Underhill had gone into shock while trying to assist.

"[He] tried desperately to help but was suffering shock," she said.

Police have confirmed the babysitter has now been charged with several offences in relation to the crash.

Matthews is expected to appear before Casino Local Court on July 20 on charges of dangerous driving occasioning death, dangerous driving occasioning grievous bodily harm, negligent driving occasioning death, and negligent driving occasioning grievous bodily harm.

The crash deeply affected the local community who rallied around the Underhill family to raise money and ease the suffering of their tragic loss.

Watch vision of the original coverage by Seven News.