Definitely the 1st one. Though you may want to add another detail to the mirror: Like a hand-print, claw marks, blood splatter or even a ghostly smile/eyes. Horror movies usually do that in their trailers and promo images. It's never usually Just a mirror alone in horror scenes.
I think some human-ish transparence red glowing eyes in the mirror would be perfect----to show the "hidden sin within", sort of thing. Like Kurogi's eyes from MHA