This may be me reading too deeply into things and/or imposing personal beliefs/experiences on the story and characters but as an example, Natori puts Diana on a pedestal as "her favorite", as in she's still just a character from the game to her
I think this somewhat reflects Diana's view of "Natalie" as well. She wants to protect her, but has shown very little understanding of what Natori is looking for, what makes her happy. In this chapter again, what made Natori's heart beat for Lapis wasn't saving her, it was telling her that she has the strength and value to learn to love herself.
This issue has been going on since they first met, and Diana does not seem to realize it (at least in both this chapter and chapter 5, she's looking at Lapis with a blank stare, but doesn't seem to understand why Natori is choosing her). I'm pretty sure it's on purpose, though. As the heroine, Diana was "written" as someone the story will write itself around for her convenience, not someone who realizes what someone else is going through.
If this is going to go away, it would probably be through Lapis herself. She is knowledgeable and seems genuinely intent on helping Diana to learn more things. I really, really wish we had more interactions between Lapis and Diana because those two characters really complement each other.