Iomedae has not, in fact, had occasion to meet with the high priestess of Shelyn since the latter inherited her title. It was around when Arazni died, and they were on the one hand desperate for powerful allies but on the other very busy, and her assessment was that the high priestess of Shelyn was unlikely, if she'd made ninth circle without crusading, to suddenly take interest in it. Crusading is not really at the forefront of Shelyn's concerns.
This, on the other hand, is. So here she is. She's in her ceremonial armor, which she dislikes the way one might dislike wearing someone else's skin but which is extraordinarily beautiful, and she bows deeply when introduced, and seats herself in a lovely chair in a lovely room in a world that is losing its battle with Evil and - tucks that thought aside, because it's not a good starting point for negotiations, to beeline straight for all of her differences with the faith of Shelyn.
She needs their help.
She closes her eyes, and explains. The whole thing, though she has told very few people in this world the whole thing. She does not particularly fear being betrayed to Tar-Baphon by the church of Shelyn, and this is not really a situation that could stand half-explained for very long.
There is another world. In the other world, it's nine hundred years in the future. Aroden is dead, Hell briefly ruled the Western Empire, there were some other problems, they've been solved, it's a long story.
Arazni was raised from the dead by Geb, nearly nine hundred years ago. She has spent all of those centuries ruling his country for him.
She's not the same. She probably no longer wants to be the person Iomedae remembers. Iomedae doesn't know what she wants. They say she is the minor goddess of despair, and empowers Rovagug cultists. Iomedae could probably kill her; it's just a question of whether Geb's retaliation would cost Good too much.
Iomedae cannot fix her. Aroden can't easily fix her, even if Iomedae brings her back to the world in which he exists. Iomedae asked. At some point the question of what it means to rescue someone who has been turned into someone else is very philosophically complicated, and separately from that it's not the kind of thing that either of them are shaped to do, and they are both of them stretched impossibly thin with their world's present struggles.
But - it's probably not as difficult as rescuing Zon-Kuthon, right.