@FgoSegul
I think what he's implying is Monte's the 'monster god', but otherwise the same as the rest of the pantheon when it comes to temples, worshiper-recruiting and so on. Naturally since Monte's not a good guy the priesthood's even more corrupt than usual, but not openly anti-people in its preaching or anything of the sort. After all, worshipers are worshipers - they're useful.
A cleric with death spells in most TTRPGs acts as a clear indicator that you're dealing with some darkass deity (the few exceptions are usually really strict cycle-of-life-and-death gravekeeper types who wouldn't tolerate someone with Mills' attitude). Mills therefore isn't some heretic or radical: just as she was happy to ignore or partake of the clergy's actions, she wants to silence Dylan for figuring it out. You can see how her mood shifts not with the accusation but when she realizes where he's going with demons having jobs and the 'feel' around them.
Probably if an adventurer of enough power climbs Monte's promotion tower, and gets a 'blessing', instead of 'Great Sage' and 'Paladin', you go all Chaos Daemon-Prince or some-such. Abandoning your humanity: "Monte's curse".
Or something along those lines.