The Idea Factory - America's Next Top Slayer

This one is a TV show that will never be made. The show starts off in a post apocalyptic world, with vampires and demons ruling everything. Main character is a teenaged girl who grew up in that world and had made deals with some of the demons to survive. After introducing the characters and the world, the big bad pulls out a woman in chains. She's his trophy, someone left over from the war that had ended the world. The last of the old slayers. The woman says something to the big bad, saying he won't be running the world for much longer or whatever. Then, the sound of a bullet being shot rings out and the woman dies. Some sniper killed her. With the last of the old slayers dead, the main character before becomes the new slayer. Suddenly, it's revealed that this is the Buffy-verse, after the fall of the old slayer gang that was spun up at the end of the original series. The sniper could become the new watcher, another storyline with him searching for the main character.