The only thing that is important to Bella is being with Edward. That is her sole focus, and while one might argue that such a singular focus is a bit unhealthy, it is also a testament to the profound depths of her love for him. At the same time, Bella here is also making clear to Edward that he is not her only path to becoming a vampire. Edward, as much as he loves Bella, has also ben controlling towards here. In this scene Bella is asserting her power to make her own life (or un-life, as the case may be) choices. That Alice—who sees the future based on people’s choices—is Bella’s other current root to vampire-hood amplifies her insistence on her ability to make her own choices.