Serial Killer Roommate

Two friends were sleeping together. One of them, who's a serial killer, woke up and noticed her friend's sexy belly. She started rubbing it and playing with her navel, who seemed to enjoy it. The serial killer then took out a knife and stabbed her friend's navel and belly. With a knife stuck in her friend's belly, the serial killer played with her friend's navel again, torturing her to death and making her vomit blood before finally dying.