Marilou Danley's sisters have said they believe she was "sent away" so she could not interfere with her boyfriend's plan to open-fire on thousands of people in the Las Vegas massacre.
Ms Danley, 62, touched down at Los Angeles Airport on Tuesday night and was escorted by the FBI who said they "have a lot of questions" after Stephen Paddock executed the sniper attack.
Speaking exclusively to Seven News, the Australian woman's sisters said they were in complete shock to discover their sister had arrived in the Philippines two weeks ago.
"I know that she doesn't know anything as well like us," one of the sisters, who chose to remain anonymous, said.
"She was sent away. She was away so that she will not be there to interfere with what he's planning."
They said Ms Danley was also wired $127,000.
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"She didn't even know that she was going to the Philippines until Steve said 'Marilou, I found you a cheap ticket to the Philippines'," they said.
"In that sense I thank him for sparing my sister's life. But that won't be to compensate the 59 people's lives."
The sisters said Ms Danley might be the only one who can "put the puzzles together" with Paddock dead.
"To be able to find out the person you love and live with can do such a thing and you thought you know the person yourself," one of the sisters said.
The 62-year-old former Queenslander was met by FBI agents at Los Angeles airport on Tuesday and will be escorted to Las Vegas.