Trudi Lenon, the Perth mother-of-three who helped murder teenager Aaron Pajich, was taken to hospital after she was attacked by a fellow inmate who poured hot water on her in prison on New Year's Day.
Lenon, 44, was in Fiona Stanley Hospital on Tuesday with severe burns after the attack at Bandyup Women's Prison at 8am Monday.
The burns to her upper body were described as serious injuries.
Lenon and her housemate, supermarket worker Jemma Lilley, 26, lured 18-year-old Mr Pajich, who had Asperger's syndrome, to their home in June 2016 on the pretext of seeing his friend Lenon's son, before stabbing him to death.
The case shocked Perth residents, with the only motive uncovered in the month-long WA Supreme Court jury trial was that it was a thrill kill for Lilley.
The trial heard how the younger Lilley was obsessed with serial killers.
She wrote a novel about a murderer called SOS, referred to herself as that and fantasised in text messages with her housemate about killing someone.
Lenon was described as an obsequious and sycophantic bondage enthusiast, who delivered her son's friend Mr Pajich to the "dominant" Lilley so she could achieve her life's ambition.
The attack on Lenon is being investigated by Midland detectives.
The women both pleaded not guilty to murder and blamed each other but a jury took less than three hours to find them both guilty on November 1 after a four-and-a-half week trial.
Pajich's body was found buried in their Orelia backyard.
They are due to be sentenced late February.