This is my sister's story from when she was about 10 years old.
During that time, we lived in Belarus. Our apartment was kind of weirdly laid out; it was one big hallway leading to the kitchen from the front door, and the doors to the bedrooms were on the left side of that hallway.
It was nighttime, everybody was asleep, and my sister woke up with an intense thirst digging at her throat.
Being 10 years old and an entire dark hallway away from the kitchen, she was too scared to go grab a drink.
All of a sudden, she sees our mother enter the room, and an intense wave of relief flows over her.
"Mama, can you please get me some water?" my sister pleaded
Mama doesn't reply, she continues to stand eerily still and look down at my sister's bed.
"Please? I'm thirsty..." my sister pleads again.
That's when "mum" disappeared. My sister described it as disintegrating into particles.
Funnily enough, rather than being scared of what just happened, she was intensely disappointed that she was not able to get a drink of water.
Explanation? We found black mold in that house, which could have caused some temporary cognitive dysfunction and caused her to hallucinate.