Ms Williams appears to be under mounting financial pressure following judgements in Melbourne Magistrates Court over bad debts, including more than $22,000 in unpaid fees to Penleigh and Essendon Grammar School.

Fairfax Media recently revealed Ms Williams is embroiled in a toxic feud over control of the estate of her father-in-law, George Williams, which has seen police take out an intervention order against the mother-of-five on behalf of George's widow.

It is also understood Ms Williams is now attempting to hawk Carl's jailhouse diaries to tabloid media outlets in a bid to profit from the notoriety of the convicted drug dealer and murderer.

Carl, who was bashed to death in prison after it emerged he had become a police informer, was buried in his favourite pair of jeans at Keilor Cemetery in April 2010.

The plot was left unmarked for nearly a year because Ms Williams claimed she was short of money.

In mid-2011, a $16,000 polished black granite headstone was installed at the grave, which paid tribute to Carl in gold-lettered writing as a "loyal loving father, husband, son & friend".

Fairfax Media understands Ms Williams paid the deposit for the monument but has repeatedly refused to settle the outstanding $10,712 bill.

"She didn't hold back. It was very significant monument with the exact design she wanted. She was very happy with it," the stonemason said.

"She kept promising to pay for it but she never did."

Ms Williams was ordered by the Magistrates Court to pay the debt in 2014 but has refused to honour the bill.

It's not the only outstanding debt left from Carl's funeral at St Therese's Church in Essendon which was attended by family, friends and a slew of Melbourne crime figures.

Fairfax Media understands a portion of the bill from the 2010 service still has not been paid to Tobin Brothers Funerals.

Sources say a number of items were also stolen during the lavish funeral by mourners-turned-souvenir hunters, including a gold crucifix that was intended to be buried with Carl.

Ms Williams' financial woes recently escalated after she was slugged with another debt judgment against her in the Magistrates Court in February.

This time it was a bill for more than $22,000 in unpaid school fees for Penleigh and Essendon Grammar School.

Roberta and Carl's daughter, Dhakota, has been a long-time student at the prestigious private school.

The revelation that Victoria Police were paying Dhakota's school fees and his father George's tax bill allegedly prompted fellow inmate Matthew Johnson to bash Carl to death for being an informer.

Ms Williams recently gained access to the computer Carl used during his time in prison following convictions for drug trafficking in 2004 and multiple murders in 2007.

Fairfax Media understands Williams is hoping to sell the materials to tabloid-style media organisations interested in printing them as a "prison diary" or using them as the basis of a potential TV show or movie.

Roberta is currently locked in a bitter dispute with the widow of George Williams, Carl's father, who died in May leaving two properties in Essendon and Broadmeadows in his estate.

Roberta and her daughter Danielle Stephens allegedly tried to force their way into the home of Kathleen Bourke during a fight over the contents of George's will, which left their Broadmeadows property to his widow.

It is understood the $760,000 Essendon home left to George's grand-daughter Dhakota will be seized by taxation authorities over a massive debt left by George.

Ms Williams and Ms Stephens, who are now the subject of intervention orders taken out by police, are claiming that an earlier will George wrote should be considered valid.

Celebrity agent Matt Ryan-Garnsey, who represents Ms Williams, did not respond to a request for comment.

Mr Ryan-Garnsey had previously told Fairfax Media that his client would contest the will and intervention orders.