The Salvation Army did not know he had been deported from Australia more than a decade ago having spent 17 months in a Queensland jail for sexually abusing a child.
He gained the woman's trust - her daughter called him "poppa" - and moved into the same apartment block.
However, the mother's suspicions were aroused when the girl asked if she was sexy and if her private parts were beautiful. When questioned, the girl said Hall had called her sexy.
The woman took her concerns to the police and Hall was charged with indecent assault on a child. He pleaded guilty to all four charges in October.
The mother described the law as "predator friendly" and Hall's offending would affect her for the rest of her life.
"He's a very good manipulator but that's what paedophiles are, they groom the parents first. I want everyone to know what he looks like and who he is so he won't be able to charm anyone else."
The woman said they had had to move home, her daughter had been forced to change schools because the children were calling her names, and counselling and transport to court appearances had stretched their budget.
Police are investigating a historical complaint against Trevor Hall.
A police spokesperson said complaints were laid in 2006 and another in 2009. However police were not in a position to comment further as the case was before the courts.
