Aside from simply being a masterful story and stunning visual experience, Guillermo del Toro’s Pan’s Labyrinth is a significant Girls Underground example.
In a way, it’s two versions of the archetype in one, mirroring each other. We infer from the beginning that Ofelia is really Something More, a return of the princess Moanna, who lived in an underground realm. Moanna was sort of a reverse GU, going from otherworld to this world (there are a few other examples of this, such as Kiki’s Delivery Service and Princess Nevermore). Having lost her knowledge and memory of herself (as many Girls Underground do at some point), she sickened and died, leaving her father to wait for her return in some other form.
Now, Ofelia is living in post-Civil War Spain, moving with her pregnant mother to the estate of her new stepfather, a vicious man. Her mother is not well, and the adults are all busy, so Ofelia is able to explore a little on her own, and one night an insect-turned-fairy guides her to a spiral staircase (at the center of a maze) leading down to a strange place. There she meets the Faun, who tells her of Moanna and gives her three dangerous tasks to complete to prove her “essence” is intact (which must be completed before the full moon, thereby giving the sense of urgency that many of these stories have).
Tiny fairies assist her now and then throughout her journeys, although some pay the price for her foolishness when she disobeys instructions and eats the food on the Pale Man’s table (hearkening back to common folklore that one should never eat the food in Faeryland). In most ways, her stepfather the Captain is the adversary, as he is cruel and violent and may keep her from her tasks. But at times it also seems as if the Faun himself is opposing her, especially when she does not act correctly.
Ofelia does not go all the way into the otherworld like most Girls Underground do, but rather straddles the divide, going back and forth as necessary to complete her tasks. The worlds bleed into each other – the giant toad with a special key lives in a tree just beyond where she lives; the Pale Man’s realm is accessed via a chalk-drawn door on her wall; her mother may be healed by a special mandrake root the Faun gives her. Magic is all around, and the only truly otherworld is the one that she (as Moanna) originally came from and may return to.
SPOILERS In the end, fleeing from her angry stepfather, Ofelia takes her newborn baby brother into the labyrinth, at the urging of the Faun. There she is told that the baby’s blood is needed to open the portal to the otherworld she came from, where she can be reunited with her true family. But she refuses, proving herself worthy. Instead, she is killed by her adversary (the most violent final showdown I think I’ve seen so far in these examples), which releases her spirit to return to her former self. And so the girl who was originally from the underground, comes back to her true home.