This answer will be completely subjective and not based out of anything but pure supposition. I think that Bella should remain a human. I know this might be a bit on the heartless side, but my reasoning is that the love between Bella and Edward acquires a heightened sensibility if they are doomed to forever be apart. It's akin to any situation where individuals in love are challenged by some type of gulf or divide. It makes their love that much more compelling and gives an obstacle for which both engage in the love of the other, but realize that it is futile. It might be as old as Homer. Part of what makes the love story between Hektor and Andromache so painful is that they both know that Hektor must die. Their love must be stronger than the forces of mortality. The love between Romeo and Juliet acquires greater magnitude when set against the forces of social bitterness and feuding between their families. In Casablanca, Rick's and Ilsa's love is so poignant because we know they will never be together. I am not trying to suggest that Edward and Bella are similar to these couples (although some claim that they are). Yet, I think their relationship acquires a greater level of depth when the desire to transcend is something of an impossible level, and in the process making their devotion to one another all the more powerful.
I think Bella has no other choice than to become a vampire, if she wants to be with Edward forever. In a normal human existence, a married couple will grow old together over a period of years, but Bella will never have that because of Edward's vampire status. The alternative to becoming a vampire is to grow old and eventually look like Edward's grandmother; although Edward says he will always want to be with Bella no matter what she looks like, this is not an alternative Bella wishes to contemplate, much less experience. Of course, Edward resists the idea of Bella changing over because he doesn't want to deny her the world of experiences she will have as a human being; he also recognizes that once Bella has changed, it is irrevocable. However, for Bella, this step into immortality is not an option, but something she needs to do to be with Edward forever as an equal-opportunity vampire.
I don't think Bella should have made just a quick decision. I feel like there are some human experiences she should have had before she decided to turn into a vampire and lose them forever.
I wanted Bella to stay human a little bit longer. While on her honeymoon with Edward, she told him that there were still a few human experiences she wanted to experience, and that she didn't mind waiting a year or two longer. That definitely would have been better for her because she would have had more time with her family and friends, and she would have had the chance to tell her parents the truth about what she wanted to become. But her pregnancy limited her days as being human. The preganancy rushed the process so much it nearly made my head spin. However, I am very happy that she can now be with the love of her life forever. She never has to worry about getting old, and neither does Edward. They will be forever young, forever beautiful, and forever in love...their happily ever after. Everything turned out for the positive in the end and that's all that matters. I was very happy about that.
yes! There is no other way for her to be with edward because if they got married one day she would look like hes grandmother