After everything that Jacob has done for Bella, I'm sure she would have feelings for him. I mean when Bella left, she was all heart-broken and all... Jacob was the one who helped her emotionally. That kind of deed is sure to have left some feelings for him. I guess 你 can call it 'gratefulness'.
Anyway Bella did mentioned:
"I could see what he saw, I knew that he was right. If the world was the sane place it was supposed to be, Jacob and I would have been together.And we would have been happy. He was my soul mate in that world-would have been my soul mate if his claim had not been overshadowed 由 something stronger, something strong that it could not exist in a rational world."
Well, if 吸血鬼 and 狼人 did not exist, she would have probably be with Jacob and not Edward.
Because when someone is nice with you, helps you, takes care of you, making his best to heal your heart, 你 can't stay indifferent. 你 get emotionally involved and 你 care about him too. From this to 爱情 there is really smal distance...
i'm pretty sure it involves renesmee. jacob and bella were drawn to each other because of her. even though she wasn't born, she was always inside of bella. (i know that sounds stupid, but the truth is that as a woman, every potential child that bella would 或者 could ever have was already inside of her.)
