Joanne Lees said she believed his missing body could still be found.
The 43-year-old returned to the Outback as part of a TV special, revisiting the place where the 28-year-old was shot.
Bradley Murdoch was convicted in 2005 of murdering Mr Falconio and assaulting Ms Lees, then 27, on a remote stretch of highway on July 14 2001.
The murder took place near Barrow Creek, about 200 miles north of Alice Springs.
The couple, from Huddersfield, were travelling when Murdoch waved down their camper van and shot Mr Falconio in the head.
Ms Lees was threatened with a gun, punched in the head and bound with cable-tie restraints before she managed to escape, hiding in bushes for hours while her attacker stalked her with a dog.
Murdoch is believed to have hidden Mr Falconio's body, which has never been found, despite extensive searches.
Ms Lees said she had "no choice" but to run from Murdoch because "it was either run or be raped and killed".
In adverts for the special edition of 60 Minutes, she says: "Pete's still missing. I know that he's somewhere here."
Asked if she is "stepping inside" her attacker's mind, she says: "I guess it is a very alien thing for me to do because I'm not a violent person.
"I'm not a murderer but if that's what I have to do and that's how I'm gong to find Pete then that's what I'm prepared to do."
She adds: "It's because I love Pete so much and I want to bring him home and I need to bring him home."
Northern Territory Police renewed its appeal to help find his remains last year.
The interview will be aired on Channel Nine in Australia at 21:40 GMT on Sunday.
The girlfriend of murdered British backpacker Peter Falconio has gone back to Australia 15 years after his death to "bring him home".