Kyuru could sense the emotions of others around her, but Myrilla could see into the very essence that made up the soul of sentient beings. Due to her nature as a Celestial, Myrilla could only accurately see one of the many aspects of the soul.
Precisely because such an aspect was her domain, Myrilla found it unheard of to see such a thing within Katya's soul. One had to know that Celestials were creatures whose nature was defined on the day they were born, precisely by the circumstances that gave birth to them; they could not change their nature.