I'm mad at my sister over a paper
What is it about the paper that's made you angry with your sister?
I needed to finish a paper and I asked her for help but she refused.
I'm sure you were frustrated with your sister, but maybe she wanted you to do it yourself? She probably thought it was best for you to work on the paper on your own so that you could learn the material.
She was supposed to do it for me. I'm going to hurt her emotionally until she does it.
Your sister wants you to succeed and she thinks it's best for you to do the paper on your own. She does not want to hurt you and wants the best for you. You have to remember that and not try to hurt her.