Diary of a Cannibal (2007)

They met on the Internet. They fell in love. They drove to the desert and stopped at an abandoned warehouse. They wandered inside. Inside they found unspeakable horror. Only one of them survived the ordeal of CANNIBAL. From a hospital bed, an injured Noelle tells shocked police detectives a tale of cannibal terror. In recounting her ordeal, the detectives learn of an even more awful truth behind the actions of this tragic couple. Horror master Ulli Lommel's depraved tale of a modern-day CANNIBAL is based on the real-life case of a man who murdered and consumed his lover -- liver and all! -- in a strange act of consensual love. In Lommel's film of the events, two star-crossed lovers enter a world where madness rules and even a loved one can transform into a flesh-eating cannibal.

Source: TMDb