Man Haron Monis's girlfriend, Amirah Droudis, has been sentenced to 44 years in prison for the stabbing murder of the Sydney siege gunman's ex-wife.

Key points: Justice Peter Johnson said Droudis "uncritically adopted and espoused Monis's foul beliefs"

Justice Peter Johnson said Droudis "uncritically adopted and espoused Monis's foul beliefs" The earliest date Droudis could be released from prison is December 22, 2047

The earliest date Droudis could be released from prison is December 22, 2047 Friends and family were overjoyed by the jail term, despite hoping for a life sentence

Droudis, 37, was last year found guilty of killing Monis's ex-wife, who can only be identified as Helen Lee, by stabbing her 18 times and setting her alight at Werrington in western Sydney in 2013.

Droudis has been given a non-parole period of 33 years.

During the sentencing hearing, Droudis sat stony faced and silent, and did not show any emotion — even when her long sentence was handed down.

Droudis chose not to give evidence at her sentencing hearing in November, but her lawyers said she was repeatedly assaulted by Monis during their relationship, which the judge acknowledged before announcing the sentence.

Droudis adopted an 'evil man's foul beliefs'

During the sentencing, Justice Peter Johnson described Monis as "an evil man" and said he clearly orchestrated and planned the murder of his ex-wife with Droudis.

The court heard she had converted to Islam due to Monis's influence, and changed her name from Anastacia to Amirah in July 2008.

Droudis had appeared in a series of "extreme and offensive" videos for Monis in 2008 and 2009, Justice Johnson said, where she had praised Osama bin Laden and "described the Bali bombers as martyrs".

"The offender uncritically adopted and espoused Monis's foul beliefs and acted in public support of him in public protests," Justice Johnson said.

He said Droudis began a relationship with Monis in that time, but that Monis was "involved sexually with a number of women apart from his then-wife 'Helen Lee'", with whom he had two children.

'Droudis wanted to form family with Monis's children'

Amirah Droudis arriving at court in 2014. ( Dan Himbrechts: AAP )

In 2012, Droudis and Monis's relationship became more serious, and the judge said a motivating factor for the murder was their desire to form a family unit with Monis's children.

Droudis had often attended child access visits where Monis asked the children to refer to her as their mother, the judge said.

While making the murder plan, Justice Johnson said Monis concocted an alibi "so contrived that it was highly incriminating of Monis in itself".

He was far away when Droudis — dressed in a hijab — waited for Ms Lee to enter a Werrington apartment complex they used for child access visits.

When Ms Lee climbed the stairs, Droudis attacked, stabbing her 18 times.

"The crime involved a frenzied knife attack which continued in spite of Helen Lee's plea for mercy," Justice Johnson said.

Man Haron Monis in an image from his own website. ( AAP )

A neighbour witnessed some of the attack and pleaded for Droudis to stop.

Droudis then set Ms Lee on fire and fled the scene.

A police officer who worked on the case, Detective Inspector Jason Dickinson, said he and his colleagues were very happy with the sentence.

"This was a brutal and callous crime and I think the sentence today has reflected that brutality," he said.

"It's never been far from the public eye, this matter, and that only serves to bring those matters back to those who have had to endure it."

The judge addressed Monis's role in the Sydney siege, in December 2014, where Monis held 18 people hostage inside the Lindt Cafe in Martin Place. Two hostages were killed during the ordeal.

Justice Johnson said Monis died "as a result of his own criminal and murderous acts".

"No-one mourns his passing and many have been left to grapple the consequences of his destructive acts," he said.

Friends 'overjoyed' by sentence

The victim's family made a statement outside the court house, delivered by a friend known as Sonia:

"Today we are very happy that justice has been served to our only daughter. We would like to thank the judge, the legal team, the DPP and the police department, and our special thanks goes to all the police officers who were involved in this case for doing a great job from day one."

Sonia said she was overjoyed by the sentence.

"I was expecting life but I'm happy with that number," she said.

"I will never forget my best friend. She was amazing. She would do anything for anyone."