Bella is in love with Carlisle and has been since the moment she met him. She knows that he is a vampire and can hurt her but she doesn't care. Their relationship becomes more intense and she asks him to change her
"Need You Now" by Lady Antebellum
The Twilight Saga New Moon
Carlisle and Bella were together and have since broken up. But, they both realize that they need each other when they're all alone.