This quote is to witty user: HakunaaMatata
Okay, you are very strong and beautiful right off the bat!!! I understand what you mean about your family. Everybody wants to be accepted. Sometimes it's like you are trying your best to get along, to make everyone happy, and even that isn't good enough! It is so frustrating! Am I right?
What you need to do is calm down first. I'm not saying you're all jacked up and not calm, I'm just saying you need to get in your zen mode first. Think about why you and your step sister don't get along. Think about why your parents seem to be taking her side all the time. This may make you mad and a little angry, but hold yourself together I know you can girl.
Tell your mom and dad, what you feel. Don't yell and accuse, because that will cause tons of tension. If they start yelling at you for not being civil with your step sister, tell them it's hard. Tell the you are adjusting to that fact she is hanging around with the wrong group. If they want what is best for her, they should tell her to rethink her options in friends. Whatever you do, stay strong, and don't get so mad that you start making others upset. (Because that's what I do). I hope this helped!!! If you need any more advice, I'm only a comment away! xoxo :))