On Friday afternoon, her uncle, Derek Barrett, 27, was arrested by NSW homicide detectives and charged with her murder. He was formally refused bail in Parramatta bail court on Saturday.  He will appear in Burwood Local Court on Wednesday.

Mr Barrett's arrest came amid rampant and tenuous speculation that Ms Leng had been communicating with an online love interest which ended in a fatal encounter after she went missing on Thursday April 21.

Instead, police believe Ms Leng - a 25-year-old Chinese international student - returned to her Campsie home on Thursday afternoon, where she lived with her uncle, aunt and cousin, after spending the day shopping in Sydney's CBD.

It is inside the family home that she was allegedly murdered.

She valiantly attempted to fight off her attacker, and suffered a number of defensive wounds, but was overpowered and killed with at least 20 stabbing blows, the autopsy revealed.

It is believed CCTV footage captured a car entering the Lake Munmorah national park, almost two hours drive from Campsie, around 7am on Sunday morning.

Inside the car, police will allege was Ms Leng's body.

Ms Leng's naked body was spotted by a tourist floating face down in the Snapper Point blowhole around 10:30am last Sunday.

She remained unidentified for three days until police matched a computer generated image of her with a missing person's report lodged by her family on Anzac Day. 

Earlier in the week Detective Chief Inspector Gary Jubelin revealed his team had thoroughly canvassed the area.

"We're very creative in the way we can capture what has gone on in the area," he said. "We are getting a pretty good understanding of what occurred in that area during that time."

Police  are now reviewing further CCTV footage to determine Mr Barrett's movements between Friday and Sunday, Fairfax Media has been told.

As police released CCTV footage on Friday showing Ms Leng's final public sighting at Campsie train station about 4.30pm on April 21, detectives quietly narrowed their focus to the family's Campsie residence.

By Friday afternoon, the Campsie home was established as a crime scene.

Earlier in the week, Ms Leng's aunt told an Australia-based Chinese-language news site her niece's Facebook chat records revealed that, unbeknownst to them, she had recently met an Australian boyfriend.

"We looked at those photos, blonde hair, white skin, his eyes were very fierce, he didn't look friendly, lives in Wollongong," she said on Thursday in an interview that has been translated.

"If this boyfriend did something bad to her, Michelle would fight back, plus she never had a boyfriend before, this is her first."

When Fairfax Media asked the NSW police on Friday whether they were pursuing this lead, a police contact confirmed it was not their main avenue of inquiry.

Ms Leng had moved to Australia from Sichuan, a province in southwest China, five years ago to study at the University of Technology, Sydney.

Her mother and brother, who are travelling to Australia in the wake of the arrest, were struggling to comprehend the news of her death, Chief Inspector Jubelin said on Friday.

"I don't think 'devastated' properly describes it. It's very difficult and even more traumatic for her family that they are so far away at this time."