Just tell your sister to mind her own business. There will always be people out there who think they know how to run your life better than you do. Reconize it for what it is--a petty power struggle. Call her on her behaviour--tell her that it is unacceptable to speak to you that way and she needs to back off and tend to her own problems. Avoid her if you can--she'll move on to another target soon enough.

Best wishes,

~Alexiel