The film positively portrays a central lesbian couple, Elena and Belén, as loving, stable, and raising a child. Their relationship is depicted with dignity and integrated naturally into the complex narrative, with challenges stemming from fate and past events, not their queer identity.

Sex and Lucía features Belén, a transsexual woman, as a complex and significant character. Her identity is revealed as a key part of her backstory, influencing relationships and plot. The film portrays her with dignity and agency, integrating her identity into the narrative without judgment or harmful stereotypes, resulting in a net positive portrayal.