You were Sally's and Lazari's unknown aunt you were always invisible so no one would know you existed. One night you weren't invisible and were tucking in Sally and Lazari into bed while they were asleep and unaware of your existence but you didn't notice Slenderman looking directly at you from the doorway, He was surprised and in awe because you weren't human a guardian to Sally and Lazari. Slenderman was quiet so you wouldn't notice him, the rest of his proxies were in their room asleep.