Dossier
Stefanie is the first person shown in Trailer 1. She is sitting across from Lucia in a correctional facility, conducting the parole interview that determines whether Lucia walks out or stays in. That's the first ten seconds of Trailer 1. Stefanie is who they chose to open with.
She works for the Leonida Department of Corrections. Her job is to evaluate the inmates under her care and make recommendations about their readiness for the street. She takes it seriously. The question of whether she takes it too seriously, or not seriously enough in the right direction, is one the narrative will answer.
She is not the antagonist. She is the system. The bureaucracy of Leonida's correctional infrastructure embodied in one person who has the authority to give Lucia the parole she is sitting there to request. That's a significant amount of power for someone introduced in the first ten seconds of the trailer.