I read somewhere that Stephenie allows the movie makers to edit the story as long as noone dies or the basic things don't change. That means - directors can't kill anyone and for example - Edward has to stay with Bella, Jacob has to be a werewolf etc. But they can change details - for example - car colors (as they changed silver Volvo to black Volvo), they can make Jacob give Bella a birthday present (dream catcher, even though there is nothing like that in book) or it is OK to make Jane blond and if they want they can make Renee asian.

Did you know that? And please correct me if I'm wrong and I apologize if I had wasted your time!