This is something that I was just thinking about- if a faerie using the AM5th edition rules really wants to harvest vitality, they should take the role of a saint, which is fairly equivalent to the ancient gods in terms of generating veneration and the ability to send people on quests.
So how would this work out in terms of realms? For example a fairy version of a saint shows up on a hillside and gives a young woman a quest- obviously the faerie gains vitality from the quest itself. If the young woman then sets up a shrine to the saint on the hillside and it starts to attract pilgrims seeking the saint, does it add to the faerie vitality or add to a divine aura? If it creates a divine aura would the faerie who inspired that worship be given an automatic right to dwell there (perhaps with a faerie regio for the saint persona?) or would the worship of the saint drive away the faerie with the saint pretense?
I go by the assumption that anything aligned to one of the other three realms is probably mimicked somewhere by a faerie. Unicorns are a borderline canonical example as both rumours of the pious chivalrous and of the more libidinous ones are reported in two different books.
Faeries might take the appearance of what people think of a demon or an angle just to get the strong emotional response that such interaction would elicit. So a Doctor Faust might be selling his soul to a demon, or might just be taken for a ride by a faerie. The unfortunate soul at the end of the day would not necessarily know the difference.
For the case of a Jeanne d'Arc who heard the voice of a faerie-angel, I would say that the hillside chapel might develop either Divine, Faerie or both depending on what form the worship takes. If people pray exclusively to the Angel, then it will be faerie, if people pray there exclusively to the Abrahamic God in orthodox/catholic/coptic (or whatever other denomination) ways, then it would lead to the formation of a Divine aura.
If the worship is a mix of the two, I would suggest the formation of both in parallel, with as ever the Divine having the aussendend, but on the nights of week divine (All Hallow's Eve, Walpurgisnacht, Easter Friday...) the Faerie would prime. I'm not a huge fan of regios, but in a game where they occur, I could certainly see a faerie regio gradually manifesting behind the divine aura.
This is something I've thought about as well in the context of saints who were definitely venerated/believed in during the 13th century, but who seem to have been entirely fictional or to have been based on earlier (non Christian) figures of veneration.
These (and I'm sure other things I haven't thought of) seem to straddle the line between faerie and the divine.
In TC&TC it talks about how it can be really hard to tell the difference between dark faerie Jinn (who lead people to sin as an incidental part of their story) and infernal Jinn (who lead people to sin knowingly out of malice). It further talks about highly cognizant dark faerie Jinn actually becoming aligned with the infernal and turning into demons.
If that's possible maybe faerie saints are something similar in reverse? They lead people to act virtuously without any real intent, but highly cognizant ones might actually start to acquire intent and align with the divine - and eventually, perhaps, become true saints.
I've always like the idea that the realms aren't as rigidly divided as magi might think, and there are such "edge cases" for any combination of two realms. We know things like Faerie Magic, Holy Magic, or Cthonic Magic can sort of align powers to two realms at once (Magic+Faerie/Divine/Infernal), so why can't the same be true for beings with might?