Jemma Lilley, 26, strangled 18-year-old Aaron Pajich, who had Asperger's syndrome, with a wire until it broke and stabbed him three times before burying him in a shallow grave in her garden.
Jemma's housemate Trudi Lenon was also arrested and convicted of murder. She too has received a life sentence.
According to court documents, Pajich's body was found in the backyard of Lenon and Lilley's shared home in July 2016. The body was in a shallow grave and covered with concrete and tiles.
At the time Lenon claimed she was only an accessory to the murder, and that Lilley was the mastermind.
A West Australian Supreme Court jury heard Lilley's motive for murder was reportedly that it was her 'life's ambition' to kill someone by the time she was aged 25.
Lilley was allegedly so 'full of herself and euphoric' after committing the murder that she boasted about it to colleagues at work.
Lilley also reportedly left incriminating voice messages to her 'obsequious and sycophantic' accomplice Lenon, talking about how excited she was and was experiencing things 'she had not felt before'.
Lilley and Lenon were found guilty after a series of phone messages were exchanged between the two discussing the murder, which were later shown to the jury.
This article originally appeared on New Idea.