Xin Ru Nun just retreated in the realm of Buddhist Law and by no means became demonized.
When she was known as Xin Ruyu within the marginal sects, she would not carelessly engage in massive killings without concern nor arrange a duel with the Master of the Stone God Palace; she would choose a secluded spot on the mountaintop to prevent innocent casualties.
She knew that sooner or later, a life-and-death battle with Shi Feiyang was inevitable, but the time had not yet come. Today she had truly only come to take away Elder Kuzhu and convert him into Buddhism.
For that reason, she did not make a move against Shi Feiyang but instead asked, "Fellow Daoist, in what form do you think Elder Kuzhu should be saved?"
Shi Feiyang replied, "Naturally, in the Daoist Dharma Body."
"The Buddhists say that sentient beings should be saved in whatever form they ought to be saved, and the Bodhisattva will appear in that very form to preach to them."