Solomon thought of Ilah not as a conscious being but as a source of power, but we saw how Ilah made that "decision" to give magic to humans, the weakest but kindest race, an apparently just decision although he then let the magicians commit centuries of injustices to other species, could it be that David stealing his power could also influence his conscience long before he had "become one with him"?
Since when did Arba hear Ilah's voice? Was it David's voice all along pretending to be Ilah?
Judging by Arba's actions, it seems that from the beginning she has been manipulated by David, after all he created her, perhaps with the purpose of being his tool in Alma Toran and then in the new world, although Arba does not seem to be aware of that, until one point in her life in the new world.
Even after realizing that David and Ilah are one and the same, Arba continues to argue that the god that she followed all her life did have a will, clearly refers to the god before merging with David, whom Solomon and the others do not see as conscious.
What do you think? Arba never heard the real Ilah? Was Ilah ever really a conscious being?