This story is pretty lazy. Every character is bland and serves as a plot device to throw every post-apoc trope in your face, just to get Woman, Boy and Girl to the cliche good ending of Hollywood. Also the monster is Boggart from Harry Potter, which was inspired by Cucuy from Hispanic folklore.

Also seeing your biggest fear doesn't make you kill yourself. Like the woman in the beginning saw her mom, and now this demon baby is supposed to make Sandra Bullock commit suicide (the one they scrapped from the movie)?

If anything, she'd laugh to death by how stupid it looks.