Iwanagahime isn't really responsible for that, she isn't to blame for what she felt.
At this point I don't blame the tsukumogami of Mayoiga anymore, in the end, they made their decision, just as much as the people of the time made their decision to exhaust many tsuku, that is the decisions people make and that led to their fates.
Even the Kami are just another piece of the karmic wheel.
And... I KNEW IT, I knew she was the one that possessed Kanaka, I have many comments on another site where I talk a lot about that, kinda obvious for years now too, but what I want to understand is Kanaka's own peculiar condition.
Kazuya's "taboo child" status is because of Iwanagahime's possession, point, but Kanaka was special in her own right, the element of her own "karma" that allowed Azami's easy possession of her is too big to not have a "name", so to speak.