My sister says mommy killed her. Mommy says I don't have a sister

My sister says mommy killed her. Mommy says I don't have a sister. My sister Lydia visits me every night. We play with dolls and tell scary stories. She's my best friend. Every time I try to tell my mommy about Lydia she yells. She hits me and throws water on my bed. Then I have to sleep in it. I don't sleep well at all. One night was too much. I was up late playing with Lydia and I accidentally let out a laugh. She stormed into my room. The sound of her walking shook the floor. I scrambled to get into bed. I didn't make it. "Who are you laughing at!?".....she growled. "Lydia." I whispered. She beat me. She laid me on the ground and threw her fists into my face. She threw me at the window leaving a spider crack from the center. I'm bloody all over at this point. Non recognizable. She finally stopped. But, I closed my eyes and I woke up in a field of sunflowers. I can't even be scared at this point, I'm at peace. I look over and I see Lydia walking toward me. "Mommy killed me when I talked about Heather. Now all three of us can play together." Lydia said while taking my hand.