I don't know how much is scripted, but I have heard through a friend of a friend who does editing for MTV that a lot of things end up on the cutting room floor and the scenes are pieced together to make them more interesting. I think they are put in a lot of scenarios to make the show have more drama. Lauren even said that MTV had Heidi show up in lots of places that she was while they were filming season 3, so they could get some catfight scenes out of it. That being said, I don't think that the girls (minus Heidi maybe) act fake for the cameras or anything. It seems like they do a great job of forgetting they are there.
Yeah even if they do that, I think most of the girls act real. Although, I read somewhere that said that Audrina was basically "cast" for the role of Lauren's friend and they hung out and have become real life friends. But initially she was cast into the show because she wants to be an actress. I don't believe everything I read though..

While Lauren was at her Teen Vogue interview, over-using the word "like", Heidi sat by the pool all day and "met" (I think it was orchestrated by MTV) Audrina. When Lauren came home, she was like, "I see you have been working hard all day, Heidi." Heidi said, "I have been recruiting friends for us!" 
Noggin is re-showing season 1 episodes? I've been dying to find re-runs but all I ever see MTV air is s2.















