She's a sumiciu (asturian folklore creature similar to borrowers). She used to live with her mother in an hórreo (a type of raised granary), surviving on the food humans would store in there. Sophie's mom left one day on a borrowing trip to the human house nearby, but unfortunately never made it back.
Sophie would have to learn to survive on her own, until shortly after she was spotted by a human during a borrowing trip to her house. Surprisingly the human not only didn't trap her, but seemed willing to accept her presence. Sophie of course fled, terrified.
A few days later there was a really bad storm and the hórreo roof collapsed, leaving the poor Sophie exposed to the rain and cold. The human would find her the following morning while inspecting the damage and rescue her. After a typical bumpy introduction, she reluctantly agreed to stay with the human until the hórreo got repaired, and that's how she met Curuxa.
She's a sweet and polite child, and loves learning everything she can.
She's a young human woman who was relocated to a village after losing her home. She got to meet smallfolk in the past, at his grandparents summer house when she was nine. Having waved off those memories as just being her childhood imaginations, she ended up developing a special interest on fairies and other kinds of tiny people.
What was her surprise when she rediscovered the smallfolk by spotting Sophie in her new home, and from that moment of she felt protective and responsible for the young sumiciu's wellbeing. Her nickname Curuxa comes from that first encounter, since sumicios usually call "curuxes" (owls) to those humans that stay awake at night and make their borrowing trips harder, which was the human's case because of her bad sleeping schedule.
Curuxa is a kind and soft spoken person with a tendency to have anxiety and panic attacks because of her recent trauma after losing her home.