Stephenie Meyer is immature because she is making a big deal out of this and over-dramatizing it instead of dealing with the fact that life is not perfect. Yes, if someone gave someone something in confidence and they leaked it to the world, they would most likely be upset. Said person would then take a deep breath and possibly a mental health day and get on with their life, which, under the circumstances would include writing the bloody book. Her excuse is that her poor little feelings are so hurt by this evil awful leak that if she wrote the book now the Cullens would lose (gee, wouldn't that be a shame...).
It's not actually that difficult to control whether or not your characters win, especially when you can look at the book with the exact same plot and go off that, nor is it hard to look at a manuscript and decide that you had better revise it because you wrote a completely different ending from the one the companion novel has. Maybe then she could be compared to either J.K. Rowling or Stephen King, both superior authors with superior books. Then again, perhaps she's so dang hurt that if she tried to write it now she'd actually produce a decent work of fiction, and we couldn't have that now could we? The universe would implode on itself if she wrote anything decent.
BUT NOW MIDNIGHT SUN WON'T BE RELEASED FOR A LONG TIME!!!!!!!!Edit
Well, a teenage writer from Miami got her novel leaked around her entire school by a teacher, most likely her Language Arts one. But she is still writing it and willing to publish it, instead of moping around and acting like the world has ended. That's right, a teenager is more mature than Stephenie Meyer, a grown adult. How sad is that?
BUT HER WORK WASN'T LEAKED AROUND THE ENTIRE WORLD!!!!!! Edit
Well, many writers had their work leaked but they still worked on it. Their fans are happy that they got to read it before it was published. SMeyer should feel the same way, if she wants to actually become a real author. J.K. Rowling also got about 2 pages of her Harry Potter and the Deathly Hallows script leaked on to the internet, and did she freak and stop? No. And SMeyer quit writing after six goddamn chapters.
Video game developers also often tend to have some screenshots of their game leaked. They don't flip out when this happens, and the fanboys/fangirls get to go home happy. SMeyer really needs to stop being a spoiled brat and learn that a leak is a fact of life and is highly unavoidable. Get over it, SMeyer!
Also, some musicians and bands have their albums leaked. In fact, Maria Brink (Vocalist for the band "In This Moment") got her album "Black Widow" leaked before it was released, and did she completely flip out and quit working on it? No, she continued working on it and eventually released it! Meanwhile, SMeyer threw a temper tantrum and quit writing simply because "Midnight Sun" got leaked onto the internet.