I would sure say so. Well, maybe not "the root of all evil" but she definitely is the cause for basically all of the characters' distress. She keeps breaking Jake's and Edward's hearts. Sure, i feel some sympathy for the girl, having to decide in between two mythical creatures knowing that whoever you choose, its going to rip the other ones heart out.
But it isnt Jacobs fault, because he was just there when Edward left. They both thought Edward wasnt coming back, he was her "new moon".
And i definitely dont think its Edwards fault. So all signs point to Bella.

Thats just my opinion and i have a feeling theres lots of other gals out there who feel the same way.
Whats your opinion on how Bella is handling her situation?