It's gonna go under a break, but it's from this game, if you're reading this please ask me some more!
Actually Aisling was born as a Cassandramancer. I didn't know she was straight and had a bad surprise in Skyhold. Here's footage on how it went in Haven:
She has a warrior/templar kink and you all can mock her.
Anyway, imagining for a moment that Cassandra had her grand moment of realisation that she was living inside a closet, I think it would have gone spectacularly wrong in the long run.
Aisling is religious. She doesn't show a lot in the Inquisition because she doesn't feel safe in being open about it. You don't exactly organize a celebration for Ghilan'nain when the whole town is convinced you're the Herald of their goddess. Plus, it doesn't fit her grand plan of people-pleasing her way up in everyone's good graces. And it really doesn't help that many people around her are pushing her to go with the flow.
The more she learns about the Chantry, the least she likes it. By the time Cullen tells her about lyrium and Templars, she has her opinion of it, and the opinion is incredibly negative.
You can see it's not a good place to be with Cassandra, and while I can see Cullen as more ready to step back and be a bit more disillusioned and open on the matter (my own personal interpretation, I don't pretend it's the right one. It's the right one for me, if any is thinking otherwise that's great!)... Cassandra isn't.
They could settle at the start not to talk about it. Aisling is *private* over her own culture, she's closed af over any of her feeling that she feels may put the other person ill at ease, that has not a solution, that may paint her in any position that could vaguely be an annoyance or a bother. So, she won't insist on the religion discourse, thinking that it'll settle, she can adapt, it's not that important.
It *is* that important, and the argument will break in the Temple of Mythal. In canon they were friends and they had a *huge* quarrel.
As girlfriends it would be worse. Cassandra's comments about the Temple are just two miles outside Aisling's boundaries. She may not like the Chantry, but she respects people believing in it and seeing that it can be helped. Her patience ends when she hears in no mistakeable terms that she's not given the same grace.
Follows a bad argument.
Follows Aisling breaking up with Cassandra.
Follows everyone being incredibly embarrassed when they're in the same room and suddenly the atmosphere gets frozen.
I don't know if they could save it, from there. If Cassandra becomes Divine, Aisling's gone, she won't stay with her, won't agree in her election. There will be a cold congratulations card out of pure courtesy.
Otherwise... If Cassandra could take a huge step back on matters of religion and become less dogmatic? There could be work to do. Maybe they'll start again but slower, could make it possibly work.
They'll need couple therapy and a lot of work between them and a common project, tho.