Evans pleaded guilty last year to murdering Ms Foreman, who died in a fire at her Corrimal home on October 27, 2011.

Ms Foreman's estranged partner Bradley Max Rawlinson and western Sydney pair Michelle Sharon Proud and Bernard Justin Spicer were also accused of taking part in Ms Foreman's killing.

All three pleaded not guilty, but Rawlinson and Proud were convicted of murder in April this year after a two-month jury trial.

Spicer will face a trial this year.

Defence lawyers representing Evans applied to the Supreme Court last week to have Evans's sentence hearing held separately to the joint hearing for Proud and Rawlinson, set down for July 3 and 4, arguing she may not receive a fair sentence without it.

The lawyers said Evans would be contesting the Crown allegation that she was "the driving force" in planning to kill Ms Foreman, as well as her role in lighting the fire inside Ms Foreman's bedroom.

They said evidence presented during the trial of Rawlinson and Proud may paint a different picture of the level of Evans's involvement compared to what she was willing to confess to.

Justice Ian Harrison rejected this, describing Evans's concerns as "more apparent than real".

"It is not in doubt that she is entitled to be sentenced only upon the facts that are agreed for sentencing purposes, or, if disputed, are properly led in evidence against her," he said.

"Provided that care is taken to ensure that I use no material in Ms Evans's sentencing proceedings that is neither agreed or properly led in her case, the administration of justice is better served if all three [sentence hearings] are conducted simultaneously."