The film was restarted half way through production after two of the original cast members left the project. The only remaining footage from this is the shot of the van pulling up to the campsite, but since you can't see them through the window, the shot was left in the film.
The rock Jennifer beats Rachel to death with in the end was a sponge covered in rock spray paint.
Approximately five minutes of footage was cut from the film, for pacing and story telling reasons.
An extended opening detailing more information on Christina's murder
A short conversation in the car after Jennifer overhears Rachel pleading with Bryan to end his relationship.
A scene of their arrival at the camp which includes Liz stumbling upon Christina's flashlight in her bag and Rachel commenting on it telling her to keep it (The phone call scene was added after this was cut). Afterwards we see Jennifer confront Bryan in the parking lot over his earlier conversation with Rachel but he brushes it off and walks away.
In a deleted scene, Bryan mentions that police claimed Christina had been killed by blunt force trauma. Most likely a "hammer or mallet..." Later in the film when Rachel knocks out Jennifer in an attempt to kill her she hits her with a hammer. This would be the hammer that was used to kill Christina.
The location where Rachel and Liz collect kindling was two miles deep in the woods. Cars were not allowed and so the only way to get there was a trailer pulled by an e-bike. Each actor and crew member were taken one at a time to the location with this method. Otherwise it would have been a 45 minute walk to and from.
