Yes, your focus should be on your sister. She needs your help! She was too young to be the one to stick up for you when your step dad was abusing you. You need to let the police know that he abused you and that he is taking care of a young girl now. You can help her like someone should have helped you.

I thought I read that you were angry at her for not recognizing the abuse? She would have been very young. That was your mom's responsibility, not your little sisters. She was too young to have that burden placed on her shoulder. You, as the elder sister should be helping her though.

She was probably reaching out to you because she was abused too.