In Ready Player One, the scene is shot in such a way to prevent the camera from seeing anything that would make it a rated-R movie, though it is still clear in the film that the woman is naked.
While the Ready Player One certainly holds on to its own PG-13 rating, the horror movie in question was originally rated-R.
And speaking of horror movie characters, there is a prolonged sequence in Ready Player One that is dedicated to a particularly popular horror movie of the 1980s.
The movie in question also contains a scene with a naked woman.