First I think you should tell a friend and talk about what your supposed to do. After that I think you should talk to an adult like your teacher. If he or she dosn´t listen to you I think you should call the police and explain the situation to them. If your parent gets mad at you, tell them that you didn´t have a choice and that it couldn´t go on like it did. After you done that I think that you should confront your sister and don´t let her escape.
Hahah, ya you could do that! :)
SvaraRadera