According to court documents cited by The Courier Mail, Julene Thorburn told her mother shortly after her arrest that she no longer felt like Rick was her husband.
“It’s hard to relate to him and treat him how I have always done. I can’t treat him any different or he will pick up on it,” she allegedly said.
“Rick loved Tiah so much and if he can do that to Tiah, he could do it to any of us.”
Police allege Thorburn killed the 12-year-old after discovering his 19-year-old biological son, Trent, had committed incest with her.
The court documents show that Julene told police Rick was home alone with Tiahleigh on the evening of October 29 - the day of Trent's horrific admission.
When she and her sons returned later that night, he allegedly told them he'd "taken care" of the situation.
"I said ‘what do you mean by that’," Julene told police in her September 29 statement according to The Australian. "Rick said ‘Don’t ask any questions, you don’t need to know I have taken care of it’.”
Tiahleigh’s decomposed body was found by fisherman on the banks of the Pimpama River on November 5 2015, sparking an intensive investigation which culminated in the arrests of four members of the Thorburn family in September.
Court documents allege that the family lied to police for several months after the high schooler's death, including during secret hearings held by the Crime and Corruption Commission. However, Julene and Josh ultimately provided a version of events to authorities in the lead up to their arrests.
Both pleaded guilty last month to perjury and perverting the course of justice, and are due to be sentenced in 2017.
Trent Thorburn has also been charged perjury and perverting the course of justice, as well as incest. He was denied bail last week and will next appear in court on February 22.