Since the Chosen of Eilistraee is a religious oriented player group, naturally there is a place to have theological discussions. That is in-game religions; please leave real-world religion out of it. Debate the fine points of a certain dogma, how a church can enforce worship while staying true to its tenets or simply why one deity is better than another one is. All are free to talk about it here.
What is Eilistraee and Selune's relationship? I've read they are allies, but little about them interacting. But I'm fairly new to Forgotten Realms, I've played NWN, but never really got into the lore until recently with BG3.
I do think Eilistraee would be so totally proud of Isobel and Aylin.
There isn't much that I know. Ed Greenwood once says that Eilistraee, Selune, and Mielikki sometimes spend time together, and her followers in Velarswood often celebrate holy rituals alongside the Selune-worshipping lycanthropes there.
You might have better luck asking directly Ed, on his twitter (@TheEdverse).
Mathematics is the art of giving the same name to different things.