20Bella Is Part-Werewolf
Bella’s resistance to the vampires’ special powers is never fully explained in the books or the movies. She has a kind of psychic shield that protects her from any mental attacks, and later on she’s able to extend this shield to protect others as well. Some have dismissed this random
ability as part of Bella’s characterization as a not-so-average "average girl." Others have speculated that Bella is actually part werewolf.
It would also explain why Jacob would imprint on Renesmee, Bella’s daughter. There’s been no indication that werewolves have imprinted on vampires or part-vampires in the past. Renesmee carrying the werewolf gene might provide a reason for Jacob’s affection for her right after she’s born.