When Angels Cry by wizardtho
Here's the summary:
When Edward tries to leave in New Moon, he underestimates both his mating bond to Bella, and her true nature's bond to him. She senses something going horribly wrong, and it forces her changes to occur. With danger at every turn, they must make it to the one place that is safe for her, but it doesn't come without a price. Find out what amazing things happen... When Angels Cry.