Upon first death, the normal dialogue sequence pops up, and asks if you want to be a demon or not. If you reject the offer, instead of letting you respawn, it just opens up the dialgoue again, and again, until you become a demon.
I am using Requiem on 2.0.0 Beta 6, Fabric Api 0.46.0, and Fabric Modloader 0.12.12. Nothing else is installed.