I'm a librarian who loves anime, manga, and reading a wide variety of genres.
"Nice objected to that idea. Since she was talking to Nick, even under these circumstances, she meticulously parsed out casual speech and polite speech to the appropriate listener; Nick received the latter."
::eyeballs and brain melting::
I'm pretty sure that this is just saying that Nice objected to Nick's idea, but that her words remained polite/formal rather than more casual (which is still an awkward way of putting it). I hate it when I'm moving happily along in this book and then stumble across a speed bump made of words.