At the Frat party, Paul and Natalie are sitting talking about what's going on. Paul puts his hand on Natalie's face and Natalie then puts her hand on Paul's wrist near his thumb. As the shot changes from Paul to Natalie, her hand appears and disappears with each shot.
When the girl is trying to escape from the gas station attendant at the gas station, she drives off with the pump still in the gas tank. The next shot of her vehicle shows a rear shot of the SUV and the gas cap is screwed back into the gas tank.
In the opening scene at the gas station, Michelle is wearing heeled black boots, but when she leaves the gas station, feet with different shoes are shown in the close-up of the pedals (which are the pedals of a much older vehicle). The shot is taken from later in the film.
When the campus police lady slips on the large puddle of blood in the professor's office, her whole back side should be covered in blood but in later scenes there is no blood on the back of her pants or coat.
Pouring rain falls when Paul, Natalie and Brenda leave campus and then stop at gas station. But few minutes later when Natalie and Brenda run from gas station in the forest grass, shrubs and trees are absolutely dry.
Blood congeals after half an hour exposed to oxygen; it is therefore impossible that the character's wrists would still be bleeding enough to soak through the white sheet that the coroner's men put on her in the morning.
In the final scene, the lead character's abdomen is seen being cut open with a scalpel. We then see her scream in pain. Minutes later, she is no worse for wear, considering the major incision in her stomach. There is no more mention of this "pain" for the rest of the film because the scene was added at the last minute.