Thank you so much you have really helped. But my parents want me to make up wit my sister but I don't know why I have to say sorry for her

If you were mean to her, than apologize. You can tell her privately that you weren't happy about her telling your parents, but you are sorry that you were unkind. She may or may not apologize for telling, but don't let that change anything. Let it go and focus on the ways you are going to work at changing to be the person you would like to be.