Sometimes....you just gotta wonder what's up with the humans round this globe. How can big people devour the little people? The further sadness comes from what your sister did. How you choose to reconcile that and deal in general, is fully up to you.
You've come to a great place for this. There's endless help here and even greater wisdom and experience. If you are about to enbark on some reconciliation and healing from it all, there's so much here for you. I hope you give it all a try...learn that you are not alone...se what has worked for others...and see that the monsters left behind for you to deal with ain't so big.