The 33-year-old went to a home in Tallebudgera, in Queensland's Gold Coast, around midday on Wednesday when she was shot in the back.
She was sitting in the passenger seat of a car and Queensland Police detectives suspect the gunshot came from inside the vehicle and went through the seat.
She remains in the Gold Coast University Hospital with a life-threatening injury, as a homicide investigation continues.
The crime scene remains in place at Trees Road and police are yet to make any arrests or recover the weapon used.
"We don't know at this point in time whether she'll survive," Detective Inspector Mark Mooney told reporters at the scene on Wednesday.
A person at the home had been moving out and the woman had arrived with a group to help, Det Mooney said.
A number of people had arrived throughout the day to collect items advertised for free on Facebook Marketplace.
Police are still searching for the shooter and the weapon used. (Dave Hunt/AAP PHOTOS)
"At this point in time we don't know who the shooter is," Det Mooney said.
"We would suspect that they would know each other, but we're open to all scenarios."
At least 10 people at the property have given witness statements but police also want to speak with anyone who was there earlier in the day.
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