“I learned this from my mom, it’s like a superstition, I think. If you’re ever in the dark, don’t look at the mirror, and I have no clue why, because she never said what would happen, just that i should “never, ever look in the mirror in the dark, because something bad will happen.” I guess it’s a ghost superstition similar to Bloody Mary, but you don’t have to say anything. Ever since then—even though I don’t believe in it—I still don’t look into the mirror when it’s dark, just in case.”
This belief is incredibly similar to the “Bloody Mary” superstition, as the informant noted. Despite not believing in the superstition, the informant still tries to not look into mirrors, which shows how deeply the belief has pervaded culture, especially within her own family.
The Guardian covers a few of the variations on the Bloody Mary beliefs in the article below.