Elizabeth Wettlaufer, the former Woodstock, Ont., nurse accused of killing seniors in her care, is expected to plead guilty to eight counts of first-degree murder on Thursday, according to a family member of one of the alleged victims.

CBC News spoke to the family member, who heard about the development during a meeting with the Crown on Wednesday.

While they were told of Wettlaufer's expected plea, there is still a slight possibility she could change her mind.

Wettlaufer's mother, Hazel Parker, told CBC News her daughter has asked that her parents not to be in court for her appearance Thursday. They were instead planning to speak to her Wednesday night by telephone from the Vanier Centre for Women in Milton, Ont.

Parker said she is sworn to secrecy about what will happen in court.

She also said her daughter has been diagnosed with bipolar disorder and is receiving medication.

"What has been lost in the media is that had Beth not come forward, police never would have known any of this. She's dealing with this the best she can," Parker said.

​Media outlets were told Wednesday in an email from the Ontario Ministry of the Attorney General that "significant developments in this case are anticipated tomorrow."

Wettlaufer, who was charged last October, waived her right to a preliminary hearing in April and instead opted to go straight to trial.

The families of the patients in the case were also told Wettlaufer is expected to plead guilty to all charges, not just those related to the deaths. The families have been given victim impact statement forms to fill out.

She faces eight counts of first-degree murder. She has also been charged with four counts of attempted murder and two counts of aggravated assault.

Woodstock, Ont., woman has been charged with killing eight elderly people at the nursing homes where she worked as a registered nurse 2:39

All of the incidents allegedly occurred between 2007 and 2014. Wettlaufer, 49, worked in long-term care homes in Woodstock, Paris, and London, often as the registered nurse in charge of the night shift.

Police have alleged that the deaths involved the use of drugs.

At a court appearance in April, Wettlaufer's lawyer, Brad Burgess, said there will "almost certainly" be a change-of-venue application to move the trial out of Woodstock because of the media attention surrounding the case.

Her lawyer did not respond to requests for comment on Thursday's proceedings.