Stephenie Meyer mentions Kristen's vampire transformation and Rob's comments about the “ridiculous” vampire sex:
MTV: Of course the fans are very excited to see Kristen's interpretation of Bella as a vampire at last.
Meyer: It's subtle and yet kind of amazing. She's very self-possessed the way she holds herself. She's a completely different kind of character.
MTV: Meanwhile Robert Pattinson has been describing the vampire sex in the film as “ridiculous” in recent interviews.
Meyer: Yeah I saw that. I think he was talking about how it was so hard to keep a straight face [during that scene]. For the actors, there are 40 people in the room and most of them are inches away from you. It's a kind of awkward menage-a-forty going on. I think when you see the scene it's a testament to their acting ability that you don't see any of that in that moment at all.