First date with some one who is obsessed help?

I'm going to go to the movie angles and demons with a girl that texts me 24/7 and is obsessed with my abs and i need help. The reason i need help is because she has been with other guys but i haven't been with a girl like this before and she has been asking what is ok with me and what isn't because im abstinent so it's making me think she might go to far. So how do i explain to her that I'm not really ready nor do i really want to go much further than just gentle kissing? If you want more info just post saying so. I really need help im going on tuesday. Oh and to any one who has seen The Da Vinci Code or Angles and Demons are they good (she said she was scared by the first one)