Merimbula author Melissa Pouliot said a new investigation into her 17-year-old cousin Ursula Barwick's disappearance that started in 2014 highlighted historical failings in solving long-term missing persons cases.

But she hopes a February 2021 inquest into her cousin's case, delayed from this year due to COVID-19, would improve the way missing persons cases are investigated in the future.

READ ALSO: Missing Persons Week: 10 missing people from the Far South Coast

"Ursula's case has highlighted a lot of areas where improvements need to be made," she said.

"Many of the mistakes police made with Ursula shouldn't have happened, but rather than dwell on the past, we really need to look at how we can learn from her to make things better for other families of the missing."

An inquest in December 2018 found Ms Barwick, who grew up in country NSW, died in a head-on collision near Tarcutta on October 27, 1987, but was buried under the name Jessica Pearce - an alias she adopted after moving to Sydney.

The confusion was partly due to an unknown person identifying her body as "Jessica Pearce" in the morgue.

In June 1988, an inquest into the death of "Jessica Pearce" was held, but was suspended due to doubts over her true identity.

Twenty-five years later Ms Pouliot published a crime fiction novel inspired by her cousin and spoke publicly for the first time about the trauma of not knowing what had happened to her.

This prompted one of Ms Barwick's school friends, Melissa Cooper, to pass on letters Ms Barwick had posted to her on September 7, 1987.

In turn, this triggered Ms Pouliot's quest to get fresh eyes onto her cousin's case, which at the time officially listed her as going missing on her birthday, August 14.

"I went around in circles after I discovered these letters trying to work out how I could get someone to revisit her case," Ms Pouliot said.

"I also had another friend from high school contact me in March 2014, Angie Miller, to let me know she'd spoken to Ursula in Darlinghurst Rd, Kings Cross, not long after she disappeared in 1987.

"This was a vital sighting that police didn't follow up at the time," Ms Pouliot claimed.

She said official records also had the wrong hair colour and eye colour for Ms Barwick.

READ MORE: The 30-year mystery of missing woman Ursula Barwick solved

Ms Pouliot said as well as close family and Ms Barwick's school friends she was fortunate to have proactive supporters from the National Missing Persons Coordination Centre, the Missing Persons Advocacy Network and the Australian Missing Persons Register.

"They helped me navigate through the bureaucracy and find new and creative ways to get attention on Ursula's case," she said.

In 2014 Ms Pouliot and her mother Dianne Panov had their first meeting with the Kings Cross detectives who had been newly assigned to the case.

"It was the first time Mum, the sister of Ursula's mum Cheree, had been interviewed by police, 27 years after Ursula went missing," she said.

She said they were fortunate the new detectives who took on the case, Kurt Hayward and Amy Scott, refused to give up until they discovered the truth.

"A lot of people believed they would never be able to solve her case and we swung from hope to despair as they pursued the possibility of foul play, then someone called Crime Stoppers with a very credible sighting which they then discovered was mistaken identity," she said.

"As it turned out, a major clue was sitting there the whole time in the letters to Melissa, where Ursula listed one of her favourite girl baby names as Jessica."

Ms Pouliot welcomed the Australian Federal Police's announcement that it had launched the country's first national DNA program, the National DNA Program for Unidentified and Missing Persons.

The program will harness modern forensic techniques to allow the advanced DNA profiling and matching of unidentified human remains and missing persons.

She said before Ms Barwick's mother Cheree died in 2004 she gave police her DNA as part of another investigation, and it was sent to the US for storage which was standard practice at the time.

READ ALSO: South Coast police, fresh search for missing Dalmeny man Ray Speechley

"Before we knew what happened to Ursula I agonised over whether her remains were sitting undetected with all these unidentified human remains, and it was frustrating that it wasn't more straightforward to try and match everything up," she said.

Ms Pouliot said her cousin was buried in an unknown plot in the Emu Plains General Cemetery and it was unlikely they would ever find her remains.

But if there ever was a way to find where she was buried it would be "really reassuring" to confirm her identity through the DNA program.

"This initiative gives hope to these families," Ms Pouliot said.

"It is never too late to find your missing person and with this new program, there is even more of a chance that more of these long-term cases will be solved.

"This is a huge step forward and I encourage anyone who has a missing family member to contact the National Missing Persons Coordination Centre to register their details."

Ms Pouliot was speaking during National Missing Persons Week, an important annual event that gives recognition that missing people are "not just one-dimensional faces on a missing person's poster".

The week is also an opportunity for families to share precious memories and reach out for new information.

"Somebody always knows something, there's always a clue out there," Ms Pouliot said.

The inquest into the disappearance and suspected death of Ms Barwick will begin at the NSW State Coroners Court on February 22, 2021 and is expected to last for three weeks.

If you have any information on a missing person call Crime Stoppers on 1800 333 000.