Lock every door by Riley Sager

Quincy is a final girl. She is the only survivor of a mass murderer who killed all her friends during their stay in a cabin in the woods. In a form of self-preservation, her memories of that night were blocked. She remembers going to the cabin and spending the day with her friends, she remembers meeting him, and then she remembers running to the road and to the cop who shot the killer and saved her life.