Every time I saw this movie that was the scene exactly as you described. Katrina is licking/tasting the boy. The boy looks up and sees her vamp out and he freaks and grabs her with his arm. Katrina pins one of the boy's arm behind his head and she grabs the other arm which the boy was using to choke her. She then proceeded to violently and swiftly smash the arm down thus breaking it. With one arm pinned and the other arm dangling broken to his side the boy was helpless to Katrina's attack. And what a pleasant attack she made on that juicy boy. As far as I know there is no edit and no longer version of that scene. However there are edited versions for TV not showing the violent arm breaking or the blood sucking.