@Kaarme
If the Eastern Hero is the one suspected of placing the curse on her in the first place, it makes sense that he would be in cahoots with the oni that we can presumably say were sent to destroy her clan while she herself was rendered completely powerless, yes?
If that's the case, IF I were the Eastern Hero, I'd definitely have left one in her immediate vicinity at all times for the express purpose of killing her if she was ever lucky enough to get the curse off. But that's only for the case that the setting requires her to be alive for something or some reasonable excuse that forces the Eastern Hero to leave her alive for so long.
If I had to guess, her Divine Possession would be a direct counter to the Eastern Hero's unique abilities.