This Ain't No Fairy Tale
If any character in this film makes us want to follow Peter Pan's lead and never grow up, it's Carmen. Because Carmen's life makes the world of adults look totally drab…and also totally depressing.
But that doesn't stop her from pooh-poohing the idea of the fairy realm.
From the very beginning we see that she has no belief in the supernatural world; she thinks that fairy tales are nonsense, and that Ofelia is polluting her mind with too much reading.
(Yeah. It's always weird when fictional parents are telling their kids that they read too much.)
And when Vidal finds the mandrake root she finally lets Ofelia have it, yelling at her:
CARMEN: Magic does not exist! Not for you, me, or anyone else!
Carmen has grown out of these silly beliefs and thinks that it's time for Ofelia to grow up too. She can't see that Ofelia needs these things…just like she can't see the Underground Realm itself. She's lost the innocence of childhood and, although she's beautiful and lovely and Ofelia adores her, she can no longer access the world that only Ofelia has the privilege of visiting.
While it hurts to watch Carmen deny her daughter something that we experience as being not only very vivid and real but also integral to her health, we also can't really blame her. It's apparent that Carmen hasn't had an easy time of it.
Her husband passed away, leaving her a single mother working in a clothing factory until Vidal married her and began providing for her. Ofelia tells Carmen she wants to "leave this place," but Carmen responds:
CARMEN: It's not that simple.
It's unclear what she means. (But that's the world of adulting for you: it's full of terrible nuance.)
Perhaps she's just referring to the fact that she's super preggo. Or that the surrounding land is dangerous or that there are just external adult complications that Ofelia doesn't understand.
Or...maybe Carmen is in a marriage she doesn't want; a marriage of necessity to a man that scares her. It's not really clear what the situation is, but needless to say that Carmen is having a rough time of it.
The Joys of Motherhood
Carmen also serves as Ofelia's portal into the life of a mother. And the portrait of she's painting of motherhood is pretty blue (or red…but let's not go there). Part of traditional feminine maturity is childbirth, and Carmen's difficult time carrying and delivering her baby scares Ofelia. In fact, Carmen comes to represent all of the pain and suffering of the adult world…just like Vidal represents its brutality.
The world of experience that Carmen lives in is frightening because there's no escape; there's no labyrinth to hide in when the real world gets tough. Ofelia's ready to deny motherhood altogether and avoid the "complications," (as Mercedes would put it) of childbirth and of being an adult woman in a world of men and war.