But if Maize is dormant in the MC’s original body , won’t she still be this naive girl in love with the hero and will do anything for him? Also since they buried the original body , doesn’t that mean that someone could fall upon it besides the demons because they found it near a human village? I like this twist in the story and I like your first theory cuz the MC has been shown able to use Divine power .
She may still be naive but, just as with that other girl who became MC's friend, Maisie could mature a little after talking to MC.
I don't think anyone would just start digging that place. The demon said it was a difficult place to come across. So, I think it would still be there unless whenever MC uses divine power, the magicians could detect her original body somehow.
WAIT. IF her original body is not affected by time in that world, she's kind of inmortal, right?
Also, I think that what will happen is
The hero tries to kill the demon king but fails because she sacrifices herself. They get her in her old body back. The hero goes mad and kills himself.
Or
She gets her old body back, the real Maisie is dormant in her own body and awakens. They get all friendly, the real Maisie goes back with the hero because she is still in love with him, makes sure that the humans leave the demons alone and whenever she's fed up with him, she goes back to the demon caste to talk with MC. Once a month they go shopping and have tea together.