Seeing Reisen being called an earth rabbit is kinda weird. But I guess it makes sense.
When Reisen learned she became tainted, she proclaimed herself to be an Earth Rabbit. It's possible the writer mistaken for thinking that all characters would call her an earth rabbit from now on.
Well, Sagume isn't calling her an "impure Earth rabbit", but an "Impure Land rabbit", Impure Land being a religious term that in this case means... well, Earth. Which of course isn't much of a distinction, but someone could argue that she's not necessarily using "Earth rabbit" as the established term and opposite of "Moon rabbit" we're used to, but just calling her "that rabbit from the Impure Land" because that's where she came from in this instance.
I did mean the translation to be a bit ambiguous on that end as well, but it actually slipped my mind that the correct term is Impure Land and not Impure Earth. Fixed that part.