Because Bella is dumb, and she clearly likes ancient, depressed Vampiri#From Dracula to Buffy... and all creatures of the night in between. rather than hot, young wolves. ;]
edward is her soulmate and she cant help that he is the one. she loves jacob too but in a different way. besides, jacob didnt imprint on her so why is he so convinced that bella is the one? i thought licantropi imprint on there true soulmate