Nicola McDonough, 23, and her mother Margaret, 52, were found at the Premier Inn in Greenock, Inverclyde, at around 7am on Friday May 10 last year.
Margaret, who was found in a bedroom, died first. Her student daughter, found in the hotel hallway, died three days later in hospital.
Police Scotland said a 31-year-old woman has been arrested in connection with allegations of fraud, reckless conduct and trying to defeat the ends of justice. She will appear at Paisley Sheriff Court tomorrow.