The switch back and forth between "Hearth Spirit" and "Hethia" depends on how formal/personal he's being. The Second Covenant, by its nature, *does* tend to reduce the level of formality, but it's not absolute.
For the other, Hethia's sense of humor is very dry, and very formal. You can tell because she answers his questions to the letter, rather than the spirit, and in a way that makes him look a little silly. If it couldn't be read either way, or if she allowed her eyes to twinkle, it wouldn't be the same kind of humor.
It looks like you figured out the humor from context well enough. In particular, the "I'm glad she's feeling better" line was, I think, reasonably clear. What's the issue, then?
For the other, Hethia's sense of humor is very dry, and very formal. You can tell because she answers his questions to the letter, rather than the spirit, and in a way that makes him look a little silly. If it couldn't be read either way, or if she allowed her eyes to twinkle, it wouldn't be the same kind of humor.
It looks like you figured out the humor from context well enough. In particular, the "I'm glad she's feeling better" line was, I think, reasonably clear. What's the issue, then?