Is this supposed to be a previous Hakurei shrine maiden?
It's YukaReimu pairing according to the author. There's more art of them at the source where she's unmasked.
the way the artist covers her face
From this image with the dream kanji the intent may be to turn it into a controlling ofuda seal. Or, considering this image, here it might just be a just a rule-of-cool menpu/cloth mask implying something spiritual (like hiding your face to eschew temptations and discard your ego). Japanese Yahoo discussions wondering about the meaning of this mask style suggest it's an import into manga/games from China or Chinese Taoism, used to mark things mystical/magical or youkai-related, but without a deeper meaning past what a given author wants it to be.