Oh, re-reading that chapter, he also mentions how Lapis was willing to give up her own life to destroy the anti-noble faction. I had completely forgotten that until we re-learned it recently.
I don't recall hearing background info in this case, but often we hear things like demihumans being rare or ghettoed in fantasy stories. Since this story takes place primarily in upper-class settings, it's likely they are excluded in most cases. Lapis relying on one may be an indication of how she is willing to break any taboo to accomplish her goal. After all, she doesn't really care if someone is a commoner or from another world, so long as they can further her plan.
So Aurora is thinking she doesn't need to be a villainess anymore? Like, I get she's an emotional teenager and all, but it's really hard to pin up her exact motivations. Ironic, since Nekotarou wanted a truly evil villainess as the MC.