A teenage girl proudly holds and award while her mother stands next to her.Lilli and Nora Berguno were driving from Canberra towards Batemans Bay when their vehicle collided with another car. (Supplied: Aniko Berguno)

A close family member of a mother and daughter killed in a crash in southern New South Wales says their loss will leave “a hole in many hearts for the rest of our lives”.

The Berguno family had been travelling along the Kings Highway at Monga on Monday, about 42 kilometres north-west of Batemans Bay, when police say another car crossed the centre line and collided with their vehicle.

A teenage girl smiles as she is about to cut a cake,

19-year-old Lilli Berguno (pictured) and her sister Phoebe were students of the University of Canberra High School. (Supplied: Aniko Berguno)

Nora Berguno, 38, and her daughter Lilli, 19, died at the scene, along with Lilli’s 19-year-old boyfriend, Jeremy.

Phoebe, 15, the only survivor in the vehicle, was airlifted to Canberra Hospital with critical injuries, where she remains.

Nora’s younger sister, Aniko Berguno, said four days after the crash that the family was still grappling with the shock of the tragedy.

“My older sister, Nora, she was honestly the best sister, friend and mother you could ask for,” Ms Berguno told the ABC.

“She would always put her kids and others first without expecting anything in return.

“She was so down to earth and genuine and there will be a hole in many hearts for the rest of our lives.”

A woman smiles while working at a computer.

Nora Berguno has been remembered as a generous mother, sister and friend. (Supplied: Aniko Berguno)

Ms Berguno first realised the crash involved her family after reading about it online while waiting for a hospital appointment.

“I heard about the accident the night before … but I never thought that it was going to be my family,”

she said.

“The next day, as I was waiting for my appointment, I read the article and it was just too similar to my family — the car, the people that were in it.”

Two women smile at each other.

Aniko Berguno (right) with her sister Nora Berguno (left). (Supplied: Aniko Berguno)

Nora’s partner, Hope Wilkins, said the extended family was focused on the recovery of 15-year-old Phoebe.

“She has a very, very long emotional and physical road ahead of her,” Ms Wilkins said.

“There are a lot of moving parts and we are taking it all day by day. We don’t really know what the road looks like ahead for her at this stage.”

Ms Wilkins said the family was grateful for the outpouring of support from the community and wanted to thank those who responded at the crash scene.

“We know they saw things that people should never ever have to see and … they did everything they possibly could in such an impossible situation.”

‘Too many deaths on that road’

The family is urging the NSW government to increase investment in the Kings Highway to improve road safety, particularly on curves and stretches with limited overtaking lanes.

a road with glass on it and men in the background cleaning

The Kings Highway at Monga was closed for 12-hours following the crash. (ABC South East NSW: Jacinta Counihan)

“There’s been too many deaths on that road,” Ms Wilkins said.

“Whilst we don’t know exactly what happened at the moment, if there are dangerous sections of that highway, we do need them fixed.

“It won’t bring our family back, but maybe their loss can help save someone else.”

School community mourns loss

Both of Nora’s daughters, Lilli and Phoebe, attended the University of Canberra High School in Kaleen.

In an email sent to the school community, the school acknowledged the fatal crash and the grief it had caused.

“Our thoughts and sympathy are with their family and friends,”

University of Canberra High School principal Kate Woods said.

“This news may be difficult for students at our school.

“We are a small and close school community, and I know we will support the families impacted by the motor vehicle incident, our students and one another at this difficult time.”

Police investigating cause of crash

Police said early inquiries suggested the collision occurred after a sedan crossed onto the wrong side of the road and struck the family’s oncoming vehicle at a possible speed of about 100km/h.

A police officer speaking at a press conference.

Inspector Will Collins says an investigation into the crash is ongoing. (ABC News: Lily Nothling)

Traffic and Highway Patrol Command Inspector Will Collins said investigators would work to determine why the car had crossed the centre line.

“It appears that the sedan has crossed onto the incorrect side of the road and struck the hatchback,”

Inspector Collins said.

A 39-year-old man and two boys, aged seven and three, were inside the sedan and sustained non-life-threatening injuries.

Investigations into the crash are continuing and police have appealed for anyone with dashcam footage from the area to contact Crime Stoppers.