She's definitely religious, but not so much as to be blind to it. She saw everything in a light similar to Sisko, who approached the Prophets in a scientific manner more than anything else. That's probably a good reason she became Kai. A sort of reconciliation between faith and science. Yes, the Prophets aren't really gods per se, but they definitely gave the Bajorans a lot of philosophical and technological insight through the orbs. A Kai who recognizes that would be a compromise of many sides of the Bajoran religion. Two other things to take into account - Kira would be like 70 at this point, so it's likely her fiery side has died down a lot. Kai Opaka gave me the impression that in her youth she used to be like Kira, so I can see Kira becoming like Opaka in her waning days. Secondly, the Kai is elected. It's not a conclave of the Vedeks, so the most religious of the candidates doesn't necessarily win. Kira probably would have lots of public opinion on her side considering all the stuff she did for Bajor as DS9's XO and such.
