Margaret McDonough and her daughter Nicola were found fatally injured at the Premier Inn in Greenock on Friday, May 10, last year.
At the time their deaths were thought to have been part of a suicide pact and police confirmed that they were not looking for anyone else in connection with the incident.
However, in the latest development in the mystery case, a 31-year-old woman has been reported to the procurator fiscal in connection with the deaths.
A spokeswoman for Police Scotland said: "We can confirm that a 31-year-old woman is the subject of a report to the procurator fiscal in connection with alleged incidents between May 2012 and May 2013."
A Crown Office spokesman said: "The procurator fiscal has received a report concerning a 31-year-old woman in connection with alleged incidents between May 2012 and May 2013.
"The report remains under consideration by the procurator fiscal."
Daughter Nicola, 23, was found unconscious by a fellow hotel guest in the hallway of the hotel at 7am, while her 52-year-old mother Margaret was found to be critically injured in a bedroom nearby.
Mum-of-four Margaret, who was a foster carer, died from her injuries on the same day the pair were discovered.
Nicola, who had a degree in social work, was rushed to Inverclyde Hospital with a deep slash wound but died in hospital three days later.
Police had been waiting to speak to charity worker Nicola in the hope of uncovering details of their final moments, and later appealed to friends and family for information about what had happened.
The pair had been reported missing 17 hours before they were found, after Margaret had failed to pick up her foster son from nursery.
It is understood that the two women were seen in their home town of Paisley on Thursday, May 9, at around 9am.
They then travelled 17 miles to Balloch, in West Dunbartonshire, and were later seen in a Suzuki Swift car, which was removed for forensic tests following the tragedy.
The pair checked in to the Premier Inn on James Watt Way in Greenock, just off the A8, at around 3.50pm the day before they were found injured. Leaving the site a short time after their arrival, they returned to the Premier Inn between 12.30am and 1am the next day and were discovered six hours later with fatal injuries.
It was revealed that the day before she died Margaret, who was a former Liberal Democrat candidate, had made a will at the offices of MSM Solicitors in Paisley.
The will instructed that her estate of £254,509, made up of the family home in Paisley, should be left to her three sons Kevin, 33, Michael, 32, and Matthew, 21.
Her daughter Nicola was not mentioned in the document, increasing suspicion that the incident was a suicide pact.
The mother and daughter were laid to rest after a service in St Mirin's Cathedral in Paisley last June.
A note in the Order Of Service read: "As people who dedicated so much of their lives to caring for some of the least fortunate children and young people in our community, we feel that Margaret and Nicola would find this a fitting tribute to their memory and, even in their passing, would allow the good work they so valued to continue."