I was under the impression that Valmafra and Delita may have been sleeping together.

Valmafra has a job class called Witch of the Coven in the data of the game, and its description implies that she wields great magical power. I think that the Church chose her to watch over Delita for a reason, and the confrontation that we see between the two in their final confrontation does not even give a hint of her true power.