The Haunting of Villa Diodati
Elise was a French nursemaid tasked with looking after William, the infant son of Mary Shelley. In June 1816, she was busy looking after William when a Lone Cyberman in search of Cyberium invaded Villa Diodati, where the Shelleys were staying. Though the Cyberman spared the infant’s life, he killed Elise and her body was found by Mary. (The Haunting of Villa Diodati)
BEHIND THE SCENES
In real life, her full name was Elise Foggi. She was still alive in 1820, by which time she had been discharged by the Shelleys and had become involved in a scandal within Mary Shelley’s family.
This is in line with the Thirteenth Doctor’s statement in the episode that she was not supposed to die.