Sara stayed in her room until Monday, locking the doors and windows. Nerezza didn’t eat, so neither would she. Her mom had screamed and banged on the door, but had not managed to get in.
The bruises from Sara’s fall had faded, but now bruises from starvation formed on the inside of her arms. She mostly slept, curled at the top of her huge bed. She drank from a water bottle stashed in the back of her closet only to keep from dying. Then on Monday morning, everything changed.
Sara woke up around 4 am on Monday. She was freezing. For late May, it should have never been that cold. She had fallen asleep with the light on, and the brightness made her rub her eyes.
She gasped in surprise as the shadows in her room pulled away from their objects. They condensed in the center of her room, forming the shape of a girl. Then they became solid, and there was Nerezza, standing there.
She looked at her hand as if to see if they were whole. Sara was pressed against her bed board, blankets pulled up to her chin. Nerezza cocked her head at her, but said nothing.
Then, Nerezza was in her closet, looking in, without having physically moved. She just appeared, leaving a trail of darkness behind her.
Then, she was at her mirror. She touched the solid surface, and it rippled like water. For a moment, her eyes flashed the same reflective sliver, and Sara knew that she could see everything the mirror had ever reflected. Sara vaguely hoped that she had never changed anywhere but her closet.
Then, Nerezza was at the bloodstained comforter. She touched it softly, and the blood disappeared. She waved her hand and the broken picture of Sara pieced itself together.
Then she sat at the foot of Sara’s bed and sighed. She turned her eyes on Sara.
“You need to eat.” She said, the first words she had spoken.
“But… I…” She trailed off. Nerezza raised an eyebrow.
“You feel no resentment towards me?”
“No. And since you don’t eat, neither will I.”
A sudden fury rose in Nerezza’s eyes. “Child, I am not mortal! You are.” She cried angrily.
“Why… why did you call me child?” Sara croaked weakly.
Some amount of softness crept into Nerezza’s face. “I often forget that I am now merely a girl. You must excuse me.”
“Is that why you talk weird?” Sara wondered.
“Occasionally.” Nerezza answered smiling, for the first time, non-evilly. “There is still much you do not know. But, for now, if you ever want to be as I am, you must stay alive.”
Pure excitement lit in Sara’s face. Nerezza touched Sara’s forehead. “Now sleep.” She said, and as Sara’s eyes closed, she saw Nerezza turn back into shadow.
Sara woke up at six, suddenly sure that she would go to school. She touched her slimy head, and decided that a shower would be nice.

I don't remember this at all. It's also been a while since I've read your stories so that also may be it.
