In episode 11, maybe. She decides to believe in Simon in order to validate her own existence. She calls herself a worthless doll, but she declares that even as a worthless doll she can still believe in Simon just like Simon believes in Kamina. Because that's what makes their lives worth living, that's what will make her a human. After Simon saves her, Nia breaks crying because her status as a person was proven. Even as a worthless doll, she still has something to fight for.

And visuals are the means to tell the story. You don't need exposition to understand the characters. You must read between lines. Shameless introspection is the reason anime is becoming so lazy nowadays.