Absolute Evil 2009 on netflix

Southern Texas. Savannah and Cooper, a young couple in love, drive through the desert in a black 70s Cadillac convertible. Unaware that they are being followed, they check into a motel at the Mexican border. When Savannah leaves to buy food, a cop sneaks into the room, pulls his gun on Cooper, accuses him of murder and tries to arrest him. But Savannah, who had become suspicious, manages to turn the tables: