It slams the social welfare system for a series of failings by social workers after Krystal made the sex abuse claims.
Coroner Morag McDowell said Krystal's new caregiver, who had been looking after her for only three weeks, was not properly informed of her fragile mental state.
The troubled girl was not given the counselling or psychological support required, the report says.
Coroner McDowell outlined a number of "missed opportunities" to manage the girl's fragile mental state.
She expressed particular concern over the care plan given to her new caregiver, which was out of date and lacked detail about her individual needs and personal history.
"Ensuring that those people taking over the parental duties of a child have all the necessary information needed to provide adequate support tailored to that particular child is fundamental," Coroner McDowell said.
CYF said it fully accepts the coroner's findings into Krystal's death.
The social worker who produced the sub-standard care plan left CYF soon afterwards, while another social worker involved in the case subsequently received extra training.
"Put simply, we failed Krystal," CYF's deputy chief social worker Nova Salomen said today.
Since the 2008 death, the government agency had made "big changes" in the ways it works with abused children "to try and prevent a failure like this happening again", she said.
It has strengthened its care plans to improve key information provided to caregivers and implemented a specific assessment tool for social workers who work with children over the age of 12.
When a child or young person was evidentially interviewed, there were now clear guidelines that required specific social work actions.
CYF has also made changes to its information systems for social workers to highlight suicide risk and critical risk checks.
The agency said gateway assessments were now being used to assess the wider needs of all children in care. CYF has now automated the scoring on those tests to remove the risk of human error.
CYF apologised to Krystal's family for its failures, Ms Salomen said.
"We agree with the coroner that this case is a reminder for social workers to focus on the needs of children rather than being process-focused."
Where to get help
• Youth services: (06) 3555 906
• Youthline: 0800 376 633
• Kidsline: 0800 543 754 (4pm to 6pm weekdays)
• Whatsup: 0800 942 8787 (noon to midnight)
• The Word
• Depression helpline: 0800 111 757 (24-hour service)
• Rainbow Youth: (09) 376 4155
• CASPER Suicide Prevention
If it is an emergency and you feel like you or someone else is at risk, call 111.
