Other mistake: Vanessa is illiterate, but easily reads the Hi-Way Café menu. (00:48:35)
Other mistake: At the end when Vanessa is sitting in the deckchair outside her Grandmother's caravan, she asks the cops if they have a cigarette. The view cuts to the cops who smile at her and chuckle; when the view cuts back to her, she grins and you can see a faint plume of smoke rising from below the camera, indicating she already has a lit cigarette. She didn't light one at any point either.
Other mistake: When Reese Witherspoon and Brittany Murphy were talking for the first time, the Hispanic girls start walking over and the caption shows that Brittany says, "Chill out alert!" but she really says, "Chola alert!" - slang for tough girl.
Answer: Police will often attempt to anger people they are interrogating, so they accidentally make a confession.
LorgSkyegon