Marilou Danley is being questioned by the FBI as the authorities seek to determine what led her boyfriend to carry out the worst mass shooting in recent US history.
Ms Danley, 62, was out of the country when Stephen Paddock rained bullets down on concert-goers on the Las Vegas Strip on Sunday night, killing at least 59 and injuring more than 500, and relatives quoted her as saying she knew nothing about his diabolical plan.
Footage shows a wheelchair-bound Ms Danley returned to the United States from the Philippines on Tuesday night and was met by agents of the Federal Bureau of Investigation at Los Angeles airport.
Ms Danley arrives in Vegas in a wheelchair. Source: 7 News
They said Ms Danley was suddenly dispatched by Paddock and wired $127,000. Photo: 7 News
Police have not described Ms Danley, who spent time living on the Gold Coast, as a suspect but Las Vegas Sheriff Joe Lombardo said Tuesday that she was a "person of interest" and law enforcement hoped she could shed some light on the investigation.
According to Australian authorities, the Filipino-born Ms Danley has Australian citizenship and has family there.
Interviewed with her face blurred so she could remain anonymous, one of Danley's sisters told 7 News she believed Paddock had deliberately sent her away.
"I know that she don't know anything as well like us. She was sent away. She was away so that she will be not there to interfere with what he's planning," she said.
No motive has emerged yet for the deadly shooting spree by Paddock, a wealthy, 64-year-old retired accountant who liked to gamble for high stakes and owned a comfortable home at a golf course retirement community near Las Vegas.
Ms Danley reportedly met Paddock through gambling. Source: AAP
It was through his gambling that Paddock reportedly met Ms Danley, when she was working as a hostess at a casino in Reno, Nevada, several years ago.
Paddock and Ms Danley shared a home in the town of Mesquite, 130km northeast of Las Vegas, where the authorities found a number of guns while searching the property.
Neighbours have said the couple mostly kept to themselves and were frequently away for weeks at a time on gambling trips.
Stephen Paddock is the man responsible for America's worst ever mass shooting. Photo: Supplied
According to ABC News, Ms Danley left the United States for the Philippines on September 15, about two weeks before Paddock checked into his room at the Mandalay Bay hotel and began the final phase of carrying out an attack that the authorities said was meticulously planned.
She is not under arrest or currently facing any charges.
Reynaldo Bustos, her brother, told ABC News that he spoke to his sister following the shooting.
"I called her up immediately and she said, 'Relax, we shouldn't worry about it. I'll fix it. Do not panic. I have a clean conscience,'" Bustos told ABC News in the Philippines.
The Australian woman's sisters said they were in complete shock to discover their sister had arrived in the Philippines two weeks ago. Photo: 7 News
Other reports have said she left the country on September 25.
Nick Suarez, a spokesman for the Philippines' National Bureau of Investigation, said the NBI was looking into reports Danley arrived in the Philippines last month, and that Paddock had sent $100,000 to her via a wire transfer.
According to The Washington Post, Ms Danley married a man named Geary Danley in Las Vegas in 1990 and they divorced in 2015.
The New York Times said both Geary Danley and Marilou Danley had children from prior relationships and that Marilou Danley has a daughter who lives in California.
"She's probably one of the most happy, outgoing, full-of-life people I?ve ever known," Dionne Waltrip, Marilou Danley's former stepdaughter, told the Times. "Everyone who has ever met her likes her."