Knowing that Victoria has come back for her, Bella believes, "It seemed to dangerous to be human. Someone like me shouldn't be human" (4.4).
She wants to speed up her transformation into a vampire, but the Cullens dismiss her concerns. They assure her that one lone vampire is no match for their clan.
While Edward is gone hunting, Bella spontaneously decides to visit Jacob. Soon after their happy reunion, though, Jacob starts beating up on Edward. He just can't understand how Bella could forgive him so easily for leaving her. She explains that Edward thought it was for her own good.
Jacob claims that if Edward hadn't returned into Bella's life, he and Bella would be together. He compares her relationship with Edward to that of a fish and an eagle. He believes vampires shouldn't exist: "Their existence goes against nature" (4.186).
When Bella reminds Jacob that he's not "natural" either, his anger fades and, behind it, Bella can see his pain:
I didn't know ho to help him, but I knew I had to try… Jacob had become part of me, and there was no changing that now. (4.199)