The troubled teen, identified as MK, had a traumatic history of sexual abuse and injected hard drugs, frequently ran away and probably engaged in prostitution in the lead-up to her death while in state care in April 2014.

NSW Department of Family and Community Services staff were questioned at the coronial inquest into MK's death on Wednesday, with revelations that she met the referral criteria to receive more intensive support, but the program was full and other children were considered higher risk.

A caseworker told the inquest that MK was the most complex and high needs child he had been assigned to look after in his 26 years of experience in the field and that she was a textbook case of traumatisation.

"She was the child who had the least reason to trust adults," he said.

The caseworker said he had discussed transferring MK's case to an intensive support team, which had greater expertise and time to deal with high needs children, but was told there were "no vacancies" so did not bring it up again.

The girl was frequently running away from the Uniting Care youth refuge Gordon House she was placed at, including going missing for seven weeks on one occasion, and adult men would visit her there by sneaking through her window.

Youth workers at the refuge could do little to stop them, and some had come to the conclusion they could not provide MK with the help she needed.

But two department staff members said there were a lack of alternative placement options and they did not want to separate MK from her younger brothers or cause further unnecessary disruption to her life by moving her.

The inquest heard that the department's highest-needs and most restrictive facility, Sherwood House, had only a handful of places and MK was not displaying behaviours that would meet the threshold for entry.

There was also limited drug and alcohol facilities available for young people who displayed violent behaviours and did not have steady accommodation.

A district director for the department, Lisa Charet, agreed with a proposition that there was not one simple change that could have made a significant difference to MK's situation, and said that the department had implemented new programs and practices following her death.

Clinical forensic psychologist Chris Lennings​ told the inquest that MK had "survival mode orientation" which arose from traumatic events that occurred early in her life and were repeated when she was in state care.

Asked if she should have been sent to a secure facility, Dr Lennings said it would have stopped the behaviour that directly contributed to MK's death but "she would have to be discharged at some point and its difficult to see how that history could have been easily overcome".

The inquest is due to continue on Thursday.