At this point, I think the author is just satirizing usual bad and overly done tropes of romance with this series. The reader was expected to react badly to the sister, only to be poked by the wife and the author by proxy.I usually like the occasional misunderstanding between characters, at least the kind without the melodrama, but the sister character feels just so forced as a source of low stakes conflict.
"A lion will kill even a rabbit with all its strength"How sad. Lions don’t see sheep as competition.