I'm going to yell at my sister for eating my food
Why would you yell at her for that?
She always takes my food when I'm not looking
I can understand why you are upset. She shouldn't take your food without asking. You should tell on her to your parents so she will stop.
She's gonna be in trouble if I tell my parents.
While it's unfortunate that she'd get into trouble, what she did was wrong. Perhaps it would serve as a good life lesson for her.