The partner of Sydney siege gunman, Man Haron Monis, has had her bail revoked on a charge of murder, with a court finding she poses an "unacceptable risk".

A deputy Director of Public Prosecutions acknowledged there had been some failings on the department's behalf when Amirah Droudis successfully applied for bail in December 2013, a month after she was charged with the murder of Monis's ex-wife.

Chief Magistrate Graeme Henson said he considered Ms Droudis's prior conviction, the nature of the alleged offence, and the remote possibility she would skip bail when making the decision to place her into custody.

"I find there is an unacceptable risk that cannot be properly mitigated by a further extension of bail," Mr Henson told the Downing Centre Local Court on Monday.

The DPP applied for Ms Droudis's bail to be revoked when, following the Sydney siege, NSW Attorney-General Brad Hazzard asked it to review the decision to grant bail.

She was charged in November last year with murdering Noleen Hayson Pal, who had been stabbed 18 times and then set alight in the stairwell of her Werrington home in April.

Last year she was found guilty, along with Monis, of sending abusive letters to the families of dead Australian Defence Force personnel. She was awaiting sentence in the ADF case at the time of the alleged murder, the court heard.

Judge Henson went to great lengths to emphasise that the allegations against Ms Droudis had not been proven and that she is entitled to the presumption of innocence.

"Decison making in relation to bail is only as good as the information provided to it," he said.

"Suspicion, wild accusation, deficiencies in evidence cannot be translated into accepted truths simply because an agency of prosecution says so or a media who wants something to be true says it must be without due process."

Deputy Director of Public Prosecutions, John PIckering, SC, earlier said that videos in which Ms Droudis endorses acts of violence, made as early as 2008, had not previously been before the courts.

"We've admitted failings about it. We are concerned that if you look at all the evidence before the court ... that there's an unacceptable risk."

Mr Pickering said the videos paired with evidence she acted under Monis's influence by the sending of abusive letters showed she should not be free on bail.

The videos, which were played after Judge Henson cleared the court, proved she held alarming views, Mr Pickering said.

"Accepting that the allegation against her is one of significant violence ... it's a concern ... that someone charged with a violent allegation holds views that can be seen by many people as extremist in nature."

In a statement, Premier Mike Baird said: "I welcome the revocation of bail for Amirah Droudis. The NSW Government expects community safety to be front and centre of all bail decisions and that is why the attorney-general expressed concern and requested a review of the case."

Monday's bail decision was made under existing bail laws, which replace the presumption against bail for serious offences such as murder with a broad consideration of whether the accused posed an "unacceptable risk" of re-offending.

The amendments to those bail laws, which the government has described as a "toughening up" - and require an accused person to "show cause" as to why they should be granted bail - do not come into effect until January 28.

Ms Droudis looked straight ahead and did not show any emotion as the decision was handed down.

She handed a blue plastic bag filled with newspapers to her step-brother John Aspros before speaking softly to Corrective Services
officers. She asked if she was allowed to wear her jewellery and then put some of her belongings in a white handbag before handing it to Mr Aspros.

Ms Droudis will next appear in court in February.