A former nurse accused of murdering two elderly women in a NSW nursing home was allegedly told they had complained about her less than 12 hours before they were found dying in their beds.

Megan Haines is charged with two counts of murder after the May 2014 deaths of Marie Darragh, 82, and Isobella Spencer, 77, and the hospitalisation of 88-year-old Marjorie Patterson.

She was refused bail in the NSW Supreme Court on Thursday, with a judge dismissing suggestions the case against her was shaky.

The court heard that all three women were residents of St Andrews Village in Ballina, in the state's north, and all had made complaints about Haines to family members and nursing home staff in the weeks before May 10.

Prosecutors allege that Haines had refused to assist one of them in going to the toilet, leaving her in bed to soil herself instead.

'You're disgusting,' the 47-year-old nurse allegedly told another, after the resident asked for help rubbing in a skin cream.

About 11.10pm on May 9, shortly after Haines arrived for her night shift, a manager at St Andrews told her about the complaints and that disciplinary proceedings had commenced.

By morning, Mrs Darragh and Mrs Spencer were unconscious in their beds, and were never revived.

Mrs Patterson, meanwhile, was rushed to hospital after complaining that she had woken in the night to find Haines administering 'unscheduled pain medication', which she believed to be paracetamol.

Justice Geoffrey Bellew refused the South African-born woman's bail application.

He added that although the prosecution's case was largely circumstantial and included no fingerprints or DNA that conclusively linked Haines to the deaths, 'it appears to be one of some strength'.

The judge said there was evidence that an ampoule of insulin that had been prescribed to another resident was found missing after Mrs Darragh and Mrs Spencer died.

Toxicology tests later indicated that both women had unnaturally high levels of insulin in their systems.

'There is evidence that the applicant was the only person who had access to medications, including insulin, which as I have outlined has been identified as contributing to the deaths of each of the victims,' Justice Bellew said.

The short, bespectacled defendant watched on via video link as her lawyer Michael Blair described the crown case as so weak it was 'barely above speculation'.

Crown prosecutor Rebecca Gray said Haines had only been working at St Andrews for two months before the alleged murders and only recently been re-registered as a nurse following an earlier suspension.

- AAP