Notice that the film looks really old. And when we go even deeper into her subconscious, the film gets grainier and scratched. And whenever we get a chance to see the present outcome of things, the film gets cut, jarringly. Also, the sound is very old, too. And it isn't until she closes off with the psychic that the music and sound becomes modern. It's almost like the movie is saying that horror cinema needs to be revived like a Leo Carrax film. The ghost in question is cinema itself, each movie an emotional imprint in time.