Does it have to be strictly either/or? Either all Marian apparitions are real or all are satanic "hoaxes?" What about the possibility of mass hysteria that is genuinely believed but has only psychological, and no spiritual, grounding? What if some are genuine, others are mass hysteria, and others are demonic?
To answer your particular concern, I would be hesitant to call any genuine Marian apparitions demonic. Would Christ allow his sacred mother to be used in such a way? And as for Satan's appearance as an angel of light, I don't think the text in question is actually referring to visions of angelic beings, but rather to the possibility that even the most extraordinarily holy persons (angelic or human) are susceptible to fall. And even if Satan wanted to use Marian for devious purposes, the Catholic Church generally investigates claims of such apparitions (and other miracles); the content of such revelations are checked against existing Catholic practice and cannot alter previous Catholic doctrine.
Could Satan use psychological means like mass hysteria to draw people away from focus on Christ, and even a proper theology of Mary (which always points to Christ), to an ecstatic Mariology focused on visions that point to Mary without pointing to Christ? Sure, I suppose it's possible. But in that case, the problem would not be with Marian devotion as such, but with the disposition of the individual- seeing Mary as an end-in-herself, not as pointing to Christ; a genuinely, for-real Marian apparition could likewise be corrupted if the person was devoted to Mary above Christ.