this could easily be a horror movie. same structure as horror
this movie follows the plot structure of many haunted horror movies and even follows the pacing of a horror movie. the structure is similar.
there might not be any ghosts and the stuff Anna is seeing might be from her memory but the movie itself almost plays off as a horror movie in structure.
i just find it interesting that if you made this movie live action, (same exact plot) and then you added some creepy elements like creepy visual or special effects or creepy music, as well as add more suspense and maybe have the party guests look more like ghosts, this would be a very common horror movie.
not even changing the script at all, just change the lighting, the mood and the music leaving the exact same dialogue and its a horror story.