Linsey Cotton, 31, was arrested and charged on Saturday with offences including fraud and culpable and reckless conduct in relation to the deaths last year of 52-year-old Margaret McDonough and her daughter Nicola, 23.
It follows a year-long probe into the mother and daughter's deaths, described at the time as a bloodbath. The pair were found at the Premier Inn in Greenock in the early hours of May 10 last year after apparently taking their own lives.
They had checked in to the hotel, 17 miles from the family home, on May 9 and spent part of the day driving around Paisley and Greenock.
The sole cause of Mrs McDonough's death was listed as "incised wounds of the left arm".
Social work student Nicola, who was found unconscious in the hallway by hotel staff, had a single wound on her left arm. She died days later in hospital.
Following the incident, detectives said they were not seeking anyone else in connection with the deaths.
However, days ago it emerged that police had reported a 31-year-old woman to the procurator-fiscal over alleged incidents between Many 2012 and May 2013.
Ms Cotton, a bar worker from Addiewell in West Lothian, has two children of her own, aged 14 and 10.
Ms Cotton is expected to appear at Paisley Sheriff Cout today.
Mrs McDonough, a foster carer and former LibDem councillor, prepared a will the day before she died, splitting her estate of £254,509 between Michael and her other sons Kevin, 34, and Matthew, 22. There was no mention of Nicola in the will.
Mrs McDonough had separated from her husband of 28 years, Thomas, in 2008.