She can't be a witch. If she was, why did Dumbledore turn her away when she asked to go to Hogwarts?<<< i'm pretty sure because he knows the future, he knew Lily would have a son and die, he knew Petunia was destend to take care of Harry
Nagini is a horcrux and can't be killed with a wand! The only reason the Sword of Gryffindor works is because it absorbed the traits of basilisk venom. Basilisk venom is one of the only things that can destroy a horcrux!