Validation of what? I can buy what Simon gets out of a relationship with Nia, but every justification I've ever seen of what Nia gets out of it very vague, probably because the series chose not to focus on her as a character for a very large chunk, and tended to use her as a plot device instead.
I'd suggest rewatching episode 11, as it's a good character development episode for Nia as well as Simon and sets up the basic points of their relationship. When Nia is told that she was created as a doll, she learns that her father, the one person who she loved and trusted, never meant for her to be her own person. But because of the things she learned while around the humans, she stands up to Guame anyway and decides to believe in Simon. Then minutes later, Simon shows up to save her, validating her belief, and tells her that no matter her past, she should live as herself. So when her father failed her and her statis as a person was put to question, Simon gave her something to believe in and valued her as an individual. Those same themes are also repeated in the second half of the story.
Re: The rage is strong with me today
I'd suggest rewatching episode 11, as it's a good character development episode for Nia as well as Simon and sets up the basic points of their relationship. When Nia is told that she was created as a doll, she learns that her father, the one person who she loved and trusted, never meant for her to be her own person. But because of the things she learned while around the humans, she stands up to Guame anyway and decides to believe in Simon. Then minutes later, Simon shows up to save her, validating her belief, and tells her that no matter her past, she should live as herself. So when her father failed her and her statis as a person was put to question, Simon gave her something to believe in and valued her as an individual. Those same themes are also repeated in the second half of the story.