The mother of slain Brisbane schoolgirl Tiahleigh Palmer says she's only halfway down the road to getting justice for her daughter.
Cindy Palmer was in the gallery of the Beenleigh District Court on Thursday as her daughter's foster brother Trent Thorburn was sentenced to four years' imprisonment.
Thorburn, 20, had earlier pleaded guilty to four charges including perjury and admitting he'd had a sexual encounter with 12-year-old Tiahleigh in the days before her alleged murder in October 2015.
Ms Palmer said hearing about the sexual relationship between her daughter and Thorburn had been difficult.
"Everything that we heard in court was a lot to hear," Ms Palmer said.
"We all know that Trent had ample opportunity to come forward with what he knew but this is just the second step in justice for Tiahleigh."
Having already served a year in pre-sentence custody, Thorburn will be released from prison on January 20 when his sentence is suspended for five years.
The sentence comes less than two months after his older brother Joshua was sent to jail for three months for his role in the Thorburn family's attempts to cover up the alleged murder.
Thorburn's mother Julene is due to be sentenced on November 3 for her role in the cover-up while family patriarch Richard Thorburn has been committed to stand trial on a murder charge.
At a pre-sentence mention of her matter on Thursday, a lawyer for Ms Thorburn said the defence still had further subpoenas to issue.
In a brief victim impact statement written for the court, Ms Palmer said Trent Thorburn had abused her daughter's trust when he was meant to be a role model for her.
"You lied and covered up the fact that you had sex with my 12-year-old daughter, and even went to the extent of coming to her funeral and dancing at the service," she wrote.
"You hugged me and my family and cried at what happened to my daughter knowing full well what you had done."