I know that is a really difficult situation. I still feel like the tips in this article can help. Have you ever heard the term, “killing with kindness?” If you keep being respectful and sacrificing your feelings while you try to be fair and kind, eventually her unfair behavior should stop. If it doesn’t, maybe a conversation would be warranted. Sometimes some MILs just do not want to change and never attempt to. I hope that is not your case. Try not to be jealous of your sister in law and just do your part. It is tough, but it can be fixed.