I love how this seems like the church had a perfectly crafted, subtle plan laid out for Aisha and Able, but the plan was TOO well-crafted to the point where they were hoisted by their own petard. Because up until the point where Aisha's father says she can't marry Hades, Aisha believes that there's no reason he and the church wouldn't approve of their engagement. After all, she has next to no mana and isn't the heir to her house, so there's no need to maintain a pure bloodline, so why shouldn't she be allowed to marry the Duke? It would only benefit her family as far as they're concerned. And why would she suspect that the pills she's taking are anything but for her health? She's always had a weak body and the last time she stopped taking them it was extremely painful, so as far as she's concerned the constant supply of pills just makes the church look kind and charitable.
But apparently her engagement was so out of left field that the church IMMEDIATELY panicked and realized that they didn't have a viable reason to stop her from marrying Hades, so they had to force her father to step in. But he's been so doting on Aisha for her whole life that she thought it would just take some light convincing on her part for him to accept her decision. Now, his blatant refusal to accept her engagement, without being able to give her a decent reason as to why he won't allow it, is making him and the church look super susp and gives her and Hades a reason to dig in and suss out their hidden agenda.
TLDR; the church's plan was TOO good and TOO subtle and they fucked themselves. I love it.