... Yeah honestly she's having trouble with any sequence of events that is at all plausible where she gets what she wants and/or Razmir gets what He wants where Infernal Cheliax stops existing, barring the fact that she, you know, wants Infernal Cheliax to stop existing. Maybe if it immediately had a coup that replaced the entire leadership with non-Infernal leadership, and it continued playing exactly the same geopolitical role without sending everyone to Hell?
Absent that - maybe they could defeat Infernal Cheliax and then immediately form a coalition of Everyone Except Cyprian against Cyprian, but, uh, actually, she's pretty sure Cyprian would want "I get to keep conquering the world" guarantees, or else want a situation where he thought he could win the war? Except that Iomedae's countries are completely useless for all military purposes except holding their borders because there's a wound in the world. (Hopefully Razmir can fix that at some point.) So in fact most of the armies that can get to the Broken Lands (that was a much better name before Galt started taking over) are either Cyprian's or Asmodeus's.
Use Cyprian to overthrow Cheliax and then immediately murder him? She's pretty sure Iomedae would not in fact do that.
Whispering Tyrant wakes up?
Aroden comes back from the dead?