Detective Chief Inspector Brendan Bernie from the Hume Police District told Sunrise he believed the alleged crime was motivated by "personal violence."
“It appears to be just personal violence-related,” he said. “We are still following up inquiries... but that is what the early indications are that I have been told.”
He added police had been told that all three women first met up at a place in Claymore, in south-west Sydney, on the evening of February 2.
“Sometime yesterday morning she was stabbed and placed in the boot,” he said. “We’ll be alleging she was in the car for several hours before she was sighted... We’ve got a few more investigative steps to take.”
Both women have been charged with wounding a person with the intent of causing grievous bodily harm, kidnapping offences, as well as taking and driving a car without the consent of its owner.
Ms Henderson was further charged with driving a vehicle without a license, while Ms Ketley was charged with driving a vehicle while disqualified and drug possession.
They remain in custody at Goulburn Police Station.