The Victorian woman, 51, was a passenger in a Ford hatchback travelling on School Road in Logan Reserve, south of Brisbane, about 9pm on Saturday when her vehicle was hit head-on by a Ford Falcon utility.
Police allege the ute, driven by a 17-year-old girl, was travelling at high speed, possibly without headlights or registration plates, while overtaking three vehicles on the wrong side of the road.
The victim, who had been returning from a family celebration, died at the scene.
Her 21-year-old niece sustained serious leg and back injuries, while a one-year-old child in the car miraculously escaped harm.
Acting Inspector Peter Venz said the "tragic and avoidable" incident unfolded as police were actively conducting a large-scale crackdown on an unsanctioned car event in the area.
"I won't comment as to whether this vehicle is linked to that hooning event; that will form part of our investigation," he said on Sunday.
"There are reports that the vehicle had no number plates on and was possibly unregistered, and there were reports that the Ford utility may have had its lights off at the time of overtaking the other vehicles."
Police are reviewing social media footage as part of their investigation.
The tragedy was among several deadly incidents to occur within 24 hours in the state, prompting a blunt warning for drivers to slow down and obey road rules.
"People just please slow down," Insp Venz said.
"Don't be in a hurry to get to where you have to go. Consider other road users … just stay safe when you get behind the wheel of a car."
The first fatality occurred about 5pm at East Palmerston in far-north Queensland after a 31-year-old man lost control of his quad bike on a local road.
His green Kawasaki struck a pole and he was pronounced dead at the scene.
Nearly two hours later, a black Honda motorbike collided with a Kia Cerato in Thornlands, about 30km southeast of the Brisbane city centre.
The 18-year-old motorbike rider died after being transported to hospital with critical injuries.
The Kia driver was uninjured.
Several other motorbike riders were killed over the weekend, including two men in a collision in the Adelaide Hills suburb of Paracombe about 2.30pm on Saturday.
On Friday, a motorbike rider was killed in a single-vehicle crash about 1.20pm on the Monaro Highway south of Cooma, in southern NSW.
A Harley Davidson rider was also killed after hitting a traffic light early on Friday morning in the inner-northern Adelaide suburb of Ovingham.
NRMA spokesman Peter Khoury said Easter was a time for people to take more care than usual on the road as they were often travelling long distances.
"They're often driving on roads that they're unfamiliar with ... so it's a different type of driving, and it requires people to be extra careful," he told AAP.
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