One of the most interesting takes on Bella that I've read is one of her as a person with an undiagnosed disability. As clumsy as she is, she's clearly got something going on there and the idea was that she's spent her entire life accidentally hurting herself and that's why becoming a vampire is so appealing to her.

The girl, as written, can barely get through the day without some fun and exciting new bruises. (And realistically broken bones with really stupid stories behind them.) The appeal of becoming a creature like the Cullen's is obvious.

I like this theory.