So my stupid step sister rejected me, but I can't let it go, how do I tackle with this?

What she thinks of you is none of your business. Family or not she does not control you or what you like or what you choose to put on your phone or face book or your . If you engage with her then you are at her level and you smear yourself with the same stupidity and filth that she smears herself with. The only way to be free of this is to turn your back and walk away. You cannot change her and you cannot allow her to change you. Luck!