Like Kamina, Nia was a character tied by the chains of her origin. Her relationship with Genome was not indented to give her any kind of "plot" relevance. It was a mimic of Kamina's infatuation with his father. Like Kamina's arc, in which Kamina faces against that same human fragility that killed Joe, Nia's arc ended with her confrontation with her father. Ultimately, she says farewell to his influence and decided to look towards tomorrow. In the end, just like Rossiu's village ends up coming to claim his soul, Nia's origin(Genome's sin of surrender against the Anti-Spiral) came to claim hers.
In a way she was an spiritual successor to Kamina, but not a replacement.