What can I do when my sister shows up after 18 years and convinces our dad that I am stealing his money?

SOMEHOW MY SISTER WENT OVER MY HEAD AND TOOK EVERYTHING. MONEY FROM THE BANK THAT WAS MINE AND MY DADS, VEHICLES.PROPERTY. AND ALL THE PERSONAL BELONGINGS. I QUIT SCHOOL WHEN I WAS 13 TO TAKE CARE OF HIM AND SHE HAS BEEN OUT OF THE PICTURE FOR 18 YEARS. SHE SOMEHOW CONVINCED MY DAD THAT I WAS STEALING AND SO HE WENT STRAIGHT TO LIVE WITH HER UP NORTH. I CANT EVEN TALK TO HIM ON THE PHONE. HOW CAN SHE HAVE WENT OVER MY HEAD AND TOOK EVERYTHING WITHOUT ME BEING NOTIFIED AT ALL. SHE JUST WANTS HIS MONEY, SHE DOESNT CARE ABOUT HIM. HOW CAN I FIGHT THIS?