She died, along with 32-year-old Jason Hill and 30-year-old Stuart Hill, when the Papillon tour helicopter came down at about 5.20pm on Saturday, the Hualapai Nation Police Department said.
Hualapai Nation Police Chief Francis Bradley says navigating the rugged terrain in the dark made it hard for first-responders to reach the helicopter's wreckage.
The circumstances surrounding the accident near the Quartermaster Canyon, about 60 miles northwest of Peach Springs, are now unknown.
The helicopter, an Eurocopter EC130 from Airbus, "crashed under unknown circumstances in the Grand Canyon" and suffered substantial damage, Allen Kenitzer, a spokesman for the Federal Aviation Administration, said in an email.
Ellie Milward, 29, Jonathan Udall, 32, and Jennifer Barham, 39, were airlifted to University Medical Centre in Las Vegas, Nevada, along with pilot Scott Booth, 42, according to Arizona Central. Rescuers were able to get to the survivors after getting assistance from military aircraft from the Nellis Air Force Base in Las Vegas. "The terrain where the crash occurred.is extremely rugged".
Witness Lionel Douglass, who was attending a wedding about 1,000 yards away, said he saw the helicopter plummet from the sky after going around in two complete circles, as if the pilot was looking for a place to land the aircraft.
Teddy Fujimoto told CNN affiliate KSNV he was in the area taking photographs when he witnessed the aftermath of the crash. Authorities say three other people died at the scene.
"Her hands were bloody and body was just more burned", Fujimoto said.
Bradley says National Transportation Safety Board officials were expected at the crash scene by Sunday afternoon to begin investigating the cause of the crash.
The company's website says it flies roughly 600,000 passengers a year around the Grand Canyon and on other tours.
The Foreign Office said it is providing support to the families of the six.
"Our top priority is the care and needs of our passengers and our staff". It also notes that it "abides by flight safety rules and regulations that substantially exceed the regulations required by the Federal Aviation Administration".
NTSB records show a helicopter operated by Papillon was involved in a deadly crash on August 10, 2001 near Meadview, Arizona.
Three British tourists were killed in the crash.