How to educate a sister who loves to beat her sister?
Observe for 2 days, see more about what she did for what, and then talk to her and let her tell you what to do; Then you can guide her reasonably, and when she asks for review, you can let her participate in the method you agreed, so that she will change slowly. Many parents can't treat their children equally, plus the encouragement of their relatives and friends; Lack of educational methods. Make a hullabaloo about and blame blindly, and eventually you will be willing to do the opposite.