I strongly believe that Bella was making an informed decision after realizing that Edward was her soul mate in every imaginable way. The Cullens, a safe and loving family, would be there to support her during the most torturous stages of the transformation. If you accept that destiny itself plays a role in the series, then Bella's theory about being uniquely suited for an immortal lifestyle with the family makes sense.
As much as Jacob wanted Bella to be human (perhaps for selfish reasons of his own), it was ultimately not his decision to make. He foolishly underestimated the weight of Bella's love for Edward, and he also refused to acknowledge that vampires could be honorable beings until the events of Breaking Dawn. If Bella is guilty of dismissing opposing viewpoints, then so is Jacob and his own biases against the Cullens. Why did Jacob not want Bella to embrace "undeath", as you say? Is it because of his inability to recognize any humanity in the Cullens, including Carlisle himself? Personally, my belief is that Jacob was prejudiced against vampires, and so he could not see that Bella would still retain her most defining characteristics after the transformation: a sense of humor, fun, loyalty, etc. And so she did.
Did Jacob have fair intentions? Yes. However, I believe that he wouldn't have respected Bella's decision, even if she was sufficiently informed and ready to do what she felt was best for
her future, and not the future that Jacob selfishly wanted her to pursue. In the series, notice how Edward is more accepting of any choice that Bella may make, whereas Jacob is too obsessed with focusing on what lifestyle that he believes is preferable for Bella.
People say that Bella is carelessly throwing her life away. However, that's simply not the case. Like Edward, she is still able to pursue an education. Stephenie even said that she easily could imagine Bella taking night classes as a student with the Cullens. Heh.
Bella's romance with Edward transcended humanity itself, and she was willing to accept the consequences of being with someone who belongs to another world entirely.
She wasn't looking at the down side of becoming a vampire. It's true he wanted her and hated the Cullens. Nevertheless, his whole campaign was an effort to get Bella to slow down her headlong rush toward vampirization and consider the benefits of staying human.
It was fruitless. He knew that. But could he really have NOT made the effort?
He made too
much of an effort. It didn't become an admirable quest to wake Bella up to an opposing viewpoint in a respectful manner. Instead, it became a quest to convince Bella to remain with Jacob, who couldn't acknowledge that vampires are still thinking beings with a great capacity for love.
As Bella said, she was growing older as Edward externally remained the same. I believe that she was aware of vampirism and its downsides, since any state of existence has both its positives and its negatives. However, she also knew that remaining focused on the positives would only make the painful transition much more bearable.
Bella's love for Edward transcended humanity itself. She was certain of one thing: she deeply loved Edward, and he loved her in return with every ounce of his being. Therefore, she was sure that committing herself to him eternally would work. It's not like there would be a chance of Edward leaving after she was turned into an immortal.
As a vampire, Bella will still be able to mature. It just won't be externally. She will still be able to interact with humans under the superb guidance of Carlisle. She could still pursue an education, since vampires have much more time to devote to educating themselves. She will be able to sexually interact with Edward. She will still be able to love Charlie. Bella is not condemning herself to a lonely lifestyle.
Bella could see that the positives overwhelmed the negatives. Jacob was only able to focus on the negative aspects of vampirism. Yet, when you think about it, the differences between vampires and humans aren't *too* significant.
Yes, vampires are stronger. Yes, they don't have the same bodily functions and weaknesses. However, vampires still love. They are able to show emotions. They are able to learn and mentally develop. They are able to create lasting friendships. Experienced vampires like Carlisle are able to normally interact with humans. Bella knew all of this, and realized that the negatives would work themselves out in the end, particularly with the humans in her life.
As an immortal, Bella still has these opportunities with the love of her life: Edward.
Does that make any sense to you guys? I've always been adamant in my defense of Bella's choices.