All three of the girls aged 14 and 15 have name suppression due to their age.
Two of them received 12 months home detention while the girl who has just been granted parole received two and a half years in a juvenile prison facility.
Grace Virtue's son Mike told Open Justice the family felt let down by the justice system.
"Our mother's life wasn't worth very much in the eyes of the justice system."
"Don't get me wrong I didn't want them hung, drawn and quartered…but for the amount of time they got, they're not going to come out any better are they?"
The girl who is set to be released next month was denied parole in December last year as the board assessed her as needing more time to rehabilitate.
The board noted that drugs, alcohol and violence had been hallmarks of her young life and she had not yet had time to address those issues fully while in prison.
The three girls initially stood trial for murder, but each pleaded guilty to manslaughter charges at earlier hearings.
According to the summary of facts the three girls targeted Mrs Virtue because she lived alone.
"Oi, u gotta come with us we've got everything we need we are ready we got a house keep your hoody on," two of the girls messaged the third on social media.
Two of them walked through a side gate and knocked on the door and asked Virtue if they could use the toilet, while the third stayed outside the property. The plan was to steal $30 so they could attend a party.
Although Virtue was initially reluctant to let them inside, she showed one to the bathroom and entered into a conversation with another in the kitchen.
On returning from the bathroom one of the girls punched Virtue in the face with a closed fist. She lost consciousness when she hit the floor, and was then kicked in the chest.
The then left with her handbag, her camera and a bank card. With payWave they purchased Chupa Chups lollipops, softdrinks, a sweatshirt and cigarettes.
Her son Michael Virtue told the court during the sentencing that the family were left feeling "empty and numb". Future moments in time with family and friends had been stolen and the family were still struggling with the senselessness of it all.
"Her kindness cost her her life ... she never wanted the limelight and would have hated every moment of being the latest news," he said.
"There are no winners. We are all losers and the biggest loser is Mum ... it all seems so pathetic."
