Esmeralda isn't supposed to follow the lights in the forest; she learns this in her very first lesson with Klara before anything has calmed down, before, even these are formally lessons and not just Klara sitting at the foot of her blankets telling her stories, telling her that she's real and she matters and she's not a monster, she belongs.
The lights in the forest are more dangerous than anything physical, more dangerous even than the shadows, Klara tells her in that voice Esme still thinks is too kind to be real, so near a song and so light for all the years and stories it carries, because the physical things and the shadows might want you but the lights can make you want so much for so long that the world whites out around you
(Greens, Esme corrects her in her head, until the world greens out around you, because she's been in the forest more recently than Klara, knows the colours that belong and those that don't -- but she doesn't say, because Klara is so kind, and she listens, because Klara's voice vibrates against her skin in sweet synchronicity with a scream that she doesn't need to voice anymore, and she welcomes the new world with arms that open wider each day she wakes to Klara making both of them breakfast.)
But the fireflies in their garden, oh, those are different, Esme knows from the first time she sees them, different from the lights in the forest, different even from the fireflies closer to the centre of Silverhojd that she grew up seeing: these, too, are part of her new world, tiny brilliant bugs that shift and dance in front of her eyes and they, too, make her want but in a way she knows is safe, in a way she feels deep in her blood that drives her out to the garden when they're the only light for kilometres around and when she stands barefoot beneath them she thinks it would be easier than breathing to fly with them.
Esme spins and spins amidst the firefly light and on the best nights Klara comes too, called by the fireflies or by Esme's laugh or just her own wanting, comes to the garden at witching hours (our hours, Esme knows now, and this is a thing that she knows she will one day find the words to say to Klara) and takes Esme's hands in her own and spins her until her feet do leave the ground and Esme is free and Esme is learning to love and be loved and Esme, too, is bursting into a hundred thousand brilliant tumbling lights.