I quite like this; it captures that weird-but-consistent internal logic of a fairytale. I also agree with Jenny—being able to make choices outside of Regular Girl's own decisions is real interesting and engaging. And again, it matches the perspective-shifting of a fairytale.
I also liked the consistency, both in terms of how my choices impacted the story but also in the frequency and style of choices; it all felt quite well put-together and planned.
My main issues were in the tenses of the piece—most of the time it was past tense, but from time to time it shifted to present and then back again. It's an easy fix, but committing to one will help a lot.
My other, larger issue is that it's not clear to me what the stakes of the story are, or how I'm positioned within it. When the demon first arrived and offered the deal, I—Regular Girl, forced to scrounge to survive—I was ready to take it (evil stepsisters exist to be punished, no?). But as the story progressed, it wasn't clear to me exactly how evil Susan and Mrs. Girl really were, or what my extra set of eyes meant, or if I even could kill Susan at all. I liked the tone, I liked the style, but the actual plot and progression seemed to meander in ways that confused me.
Still, overall, you've got a strong basis here and an excellent hook.