Jeremy
First of all, she is going to find out. That's the thing with having the same dreams.
Second, you are only getting started, so if you think this is bad, strap on the seatbelt.
Third, quit acting like a douchebag to your sister. She is your sister. She wants you around, and you haven't done a damn thing but push her away. Your parents died. Don't take it out on the living.