Tiffani Scholten was found unresponsive after emergency services were called to her Coomera home. She was later declared dead.
This week, Queensland Police detectives arrested a 37-year-old man and a 36-year-old woman and charged them both with murder.
Police will allege they are both known to the child.
A spokesperson from Queensland Police’s Vulnerable Persons Unit praised the dedication of officers after the “extensive investigation”.
“The investigation into the death of this young girl has been one of the most heart-wrenching and complex we’ve had to conduct,” Detective Inspector Paul Fletcher said.
“From the moment the investigation commenced, our priority has been to seek justice for this innocent child, who was tragically failed by those known to her.
“It is deeply distressing to investigate the death of any child, but the circumstances surrounding this case have been particularly confronting for our officers.”
Fletcher said detectives had worked diligently, using every resource to close the investigation and “ensure that those responsible face the full weight of the law”.
He said that background investigations due to medical complications added to the length of the investigation.
Fletcher also acknowledged the impact the case has had on the community and those close to the victim.
“We understand the grief and pain this has caused the community, and we hope these arrests bring some level of comfort to those who knew and loved this young girl. While nothing can undo the tragic loss of life, we are committed to ensuring justice is served,” he said.
The 37-year-old man and 36-year-old woman were due to face Southport Magistrates Court today.