Ms Danley is now in U.S. federal agents' custody, and investigators will want to know if she can shed any light on why Paddock carried out the worst mass shooting in recent USA history.
Investigators say that the shooting rampage was meticulously planned and included specially modified weapons. FBI Deputy Director Andrew McCabe told CNBC on Wednesday that the lack of a clear motive was a "surprise" in this mass shooting.
Baristas told the paper they would wince when Paddock came in with Marilou Danley, because he regularly belittled and berated her in front of customers and staff.
Authorities investigating the mass killing may look to a "psychological autopsy" to try to uncover what led Paddock to open fire into a crowd at a country music concert.
The girlfriend of the Las Vegas gunman is set to be interviewed by authorities.
She was expected to be questioned upon her arrival in Los Angeles, the New York Times reported.
Mendoza said they always ordered the same drinks - a venti mocha cappuccino for him and a medium caramel macchiato for her. "She was away so that she will be not there to interfere with what he's planning", one of her sisters in Australia told local reporters.
"No-one can put the puzzles together".
"Only Marilou can maybe help".
Details on the gunman who killed 59 people at a Las Vegas festival have been revealed.
"He's a sick, demented man", Trump said. This investigation has not ended with the demise of Mr. Paddock. In the days before the attack, he was holed up in a suite at the Mandalay Bay hotel, located on The Strip.
'The investigation with her is ongoing and we anticipate some information from her shortly. The shooting went off and on for nine to 11 minutes, he said.
Paddock smuggled a cache of 23 weapons into the hotel, including AK-47s and "bump stock" devices to make his guns fully automatic, in 10 separate bags.
A bill has been unearthed suggesting Las Vegas shooter Stephen Paddock had someone else in the hotel room with him.
After Paddock gunned down the concertgoers, he then turned a gun on himself.
'It's a very, very sad day for me personally, ' he said.
Paddock's violent transformation has mystified everyone - his brother, investigators and the families he victimized.
Immigration documents in the Philippines say that Danley first arrived there on September 15, departed on September 22 then returned three days later on a flight from Hong Kong.
She and Geary Danley reportedly divorced in 2015 and she was living with Paddock in Mesquite, Nevada, 130km from Las Vegas.
Paddock's brother, Eric, has said he was mystified by the attack.
Stephen Paddock, a reputed heavy gambler, allegedly wired almost $100,000 to the Philippines prior to the shooting in which he took his own life. Authorities have not yet determined the exact date or goal of the wire transfer or who the recipient was.
She is believed to have one sister still living in Australia.
The sisters, who were not identified by name and whose faces were blurred, added that Danley would willingly cooperate with investigators.
Matthew Lombard, a Los Angeles attorney hired by relatives to represent Danley, declined to comment.
They show semi-automatic assault-style rifles on the floor and on furniture.
The guns were bought in Nevada, Utah, California and Texas, said Jill Snyder, special agent in charge of ATF field division in San Francisco. Investigators also learned Paddock accompanied Danley on a previous trip to her home country.