Throughout the movie it appears that she is going to be another victim of a group of snuff film makers, only at the end to reveal that she is actually part of the group, and has helped lure people to their deaths.
At the start of the movie she and two male friends break down in their car outside a creepy house and knock on the door to use the phone. They are invited inside and end up getting drugged and taken off to have their death filmed. A short time later a female snuff film maker appears, she puts a video camera in a tied up Ruby’s hands and makes her record the murder of one of her friends.
Much later in the movie, Ruby and the surviving male friend are made to run through an abandoned prison, avoiding people out to get them, and trying to escape from their captives. Eventually Ruby and the man manage to get quite far away and make it outside of the prison to their apparent freedom.
However, before the two can fully escape, Ruby’s evil nature comes to light as she turns a gun on her supposed friend. She makes him get on his knees before her and tells him with a wicked grin “This is your big scene, are you nervous?”. Before the man has time to fully digest what is going on, the female snuff gang member from before shows up and stabs him in the back. The man starts to collapse as Ruby does a small celebratory dance. A male member of the snuff film gang shows up and its revealed that Ruby is his daughter. He hugs the two women and they all seem pleased with the footage they have.