The trio came up for parole last year, just a decade after going to prison. Regular parole hearings have created fresh pain for the Mullins family who have attended five this year and face two more in February.
They have told the Parole Board they want the killers to stay in prison.
As part of the release process, the family had exercised its right to refuse any communication from the killers.
Yvonne Mullins, the victim's sister, said she was astounded when a letter arrived from Natalie Fenton.
In the letter, stamped as having passed through the Parole Board, Natalie Fenton wrote: "My life before jail was based on survival. I didn't believe there was a God because I believed I was God. The knowledge of what I have done will be with me for all eternity."
But she also referred to Mullins as "Miller".
"It just goes to show how sorry she is if she can't even get his name right," said Leigh-Anne Mullins, the victim's daughter.
There was further upset when the Mullins were called by prison staff to be told Katrina Fenton was being freed to display some of her prison art.
Both Leigh-Anne and Yvonne were left with the impression they were being invited to attend. After raising the issue at a parole hearing, the Parole Board ordered another inquiry.
Also frustrating was learning that Katrina Fenton made more than 50 visits outside the prison without the family being told.
"It's all just box-ticking and a lack of communication," said Leigh-Anne. Yvonne said each parole hearing felt like they were battling the system. "We feel like we are going along to fight for our justice."
The family have been supported by the Sensible Sentencing Trust. Spokesman Garth McVicar said the system needed to try harder to deal with people as real human beings.
Parole Board spokeswoman Sonja De Friez said the board apologised to the Mullins family for the letter which should not have been sent.
"We are extremely surprised that this has occurred and are taking this very seriously."
Corrections communications adviser Jean Archer said no staff would be interviewed on concerns by the Mullins family over the lack of a personal touch.
In a statement, she said there was no invitation extended to the exhibition. Instead, the phone call was made to alert the family that Fenton was out.
"Public safety is our top priority and we take victims' rights seriously."