To protect Sophie, the siblings and Bret stay overnight at the house, turning on every light to hold Diana at bay. However, Diana cuts the power, trapping Rebecca and Martin in the basement. Bret escapes and calls the police.
When Diana corners Rebecca and prepares to kill her, Sophie realizes that she is Diana's only link to the human world. To save her children, Sophie sacrifices herself, causing Diana to permanently vanish.
Diana’s spirit attached itself to Sophie, manipulating her fragile mental state to stay tethered to the living world. The Climactic Showdown
