Because Rosalie told Edward that Alice told her that Alice saw Bella jump off a cliff and drown. But Alice couldn't see Jacob saving Bella, because by then he was already a werewolf. And Alice can't see any future to anyone if it involves a werewolf.
Probably Jacob is a werewolf, but Jacob loves Bella he wouldn't hurt her.
Jacob is a werewolf who is in love with Bella. He hates Edward. So to answer your question hes a werewolf
Alice Cullen
She has to choose between Edward and Jacob and she chooses Edward after she finds out Jacob is a werewolf and his friends.
To sum it up - Edward leaves with the reast of his family, Bella goes into depression, Vella befriends Jacob, Jacob becomes a werewolf, Bella jumps off a cliff, Alice comes back to Forks, and finds out edward is going to committ sucide, Alice and Bella go to Italy to save Edward, Edward is saved, Bella now has to become a vampire before the Volturi come looking for her.
The four most important characters in Twilight are Bella Swan, Edward Cullen, Jacob Black, and Alice Cullen. Bella is the protagonist, Edward is her vampire love interest, Jacob is a werewolf and Bella's close friend, and Alice is Edward's vampire sister with precognitive abilities.
He calls him Jake like Bella, Dog (because he is a werewolf), Jacob Black and Jacob.
Edward (and everyone else) leaves (for exactly 378 pages). Bella gets depressed. She then sort of comes out of her depression by hanging out with Jacob. Jacob re-builds two motorcycles and when they first ride them Bella starts having hallucinations of Edward's voice. Jacob turns into a werewolf (shape-shifter) and becomes distant towards Bella. Bella looses it and jumps off of a cliff. Jacob rescues her but Alice has a vision of Bella jumping but not of her being saved because she can't see werewolves. Alice tells Rose, who (not understanding) tells Edward, who runs off to Italy to try and provoke the Volturi into killing him. Alice goes to Forks to see Bella. While Jacob is at Bella's house (Alice isn't there yet) Edward phones. Jacob does not recognise Edward's voice and mistakes him to be Carlisle but not before Jacob tells him about the funeral (for another dude). Alice shows up, finds out about the phone call, and she and Bella speed off to Italy. In Volterra, Bella is re-united with Edward, but the Volturi are already there and Alice, Bella and Edward are taken to the Volturi's evil underground lair. There the Volturi reason that Edward will not make a nuisance out of himself and let them all go (But not before Jane had her sadistic fun). Basically they go home, reunite, and everything's fine again.
Well, Bella sleeps in all day, then Edward gives her a hand me down charm to put on her bracelet. Bella then finds out Jacob is second in command in his pack, and that Leah clearwater became a werewolf. Then Alice comes to babysit Bella while Edward talks to Jasper. Then Edward kidnaps Bella.
Edward leaves Bella, thinking she will be better off without him. Bella finds her she becomes very close friends with Jacob, who turns into a werewolf. Bella runs into Laurent hiking while he was hunting, he tells Bella that Victoria wants her dead for Edward killing her mate James. Bella hears Edwards vioce everytime that she is in danger, so she dives off a cliff. Alice sees her and tells Rosalie, who tells Edward. Edward thought that she was comitting suicide and succeeded. He cant live without her and tries to get himself killed, but Bella and Alice find him in time.
Edward Cullen doesn't like Jacob because Jacob is a werewolf. Jacob also doesnt like Edward. Billy(Jacob dad) wants Bella to break up with Edward. Billy paid Jacob to go to Bella dance and talk to her about breaking up with Edward. Edward also doesnt like James. Who try to kill Bella in Twilight.