I scared the demoness off when I lied. Is she gone forever?
At the moment, we do not have a clear answer to this question. Since the plot part is still completely unknown.
If you doubt your decision (to lie) and you did it less than 3 game days ago, then you can go back to the autosave and make another choice.
But in general, in any RPG, be sure to make a separate save in those places where you doubt the choice. Since many such games of this genre operate on the principle of "if the user made the wrong choice, it is his fault."