The rule is that “Artha spent on an Aristeia counts for an Epiphany” (p 69) so RAW it goes somewhere.
Tugging on my lawyer’s cap for a moment, that destination turns on the word “an”: is it merely grammatical or is it intended to be permissive, i.e. an active statement that the player may put that Artha toward an Epiphany rather than the usual rule of Artha going toward the Epiphany of the tested ability.
Assuming the rules do intend a player may pick which Epiphany it advances, the question is whether that is a limited choice. While the rules are not explicit (hence @CarpeGuitarrem’s question), Divine Aura requires a specific goal, so it would not be a stretch to say the Artha goes toward an ability tested in pursuit of that goal.
A narrower variant is that the the Artha goes toward the most crucial ability in pursuing the goal, and thus the rule says an Epiphany because the recipient ability isn’t always the same.
While the most contentious legal cases tend to be those over whether one situation is analogous to another, this has the benefit of being both a simple answer and a close analogy. One could argue the rule states it only applies to Fate and Persona expenditure, so the analogy only applies to the Fate and Persona expenditures for Divine Aura; however, that would both leave the destination of Deeds expenditure less than explicit and complicate the situation.
Given that both the game world and the methods of gathering Artha are defined by player’s expectations of what sort of game they want to play (c.f the things a ~wise skill can add being defined by what players think fits the world), this could be a rule that resolves into either case based on what the overarching game ethos is: going to Health fits a game where the focus is on survival against the odds; going to a situation-appropriate ability fits a game where the focus is more on great deeds netting great rewards.