The trio will be sentenced on 13 November.
Yesterday, Virtue's granddaughter, Samantha Virtue, told the court her grandmother's health had been deteriorating in the days leading up to her death.
Fighting back tears, she told Crown prosecutor Ben Vanderkolk her grandma had described one of the teens in vivid detail.
"She said 'that young girl had pure evil in her eyes'," she said.
Virtue's daughter-in-law, Jennifer Virtue, had known the victim for decades.
She said the 90-year-old called a spade a spade and loved her family to bits.
"She was a beautiful caring woman who loved nature and loved her family," she said.
Jennifer Virtue said her mother-in-law had a bright outlook and a huge compassion for others.
Crown prosecutor Ben Vanderkolk told the court the teenagers' main goal was to get money - they had targeted Virtue's home because she was elderly and lived alone.
"The three young women wanted and needed money - they had identified a house - it had a vulnerable occupant ... they were armed with at least one or two lethal weapons," he said.
He said two of them went inside while a third was on the lookout outside.
He said Virtue was assaulted and her handbag was taken.
"Mrs Virtue's debit card was then used to buy three Chupa Chups, drinks, a hoodie, a pair of jeans and tobacco.
"The card declined on attempted purchases of more cigarettes and alcohol," he said.
