It definitely became clear to me by the end that the concept of being different and unique were what made you desirable. Though throughout the story, I'm not sure if I got enough context to fully understand why not being unique would lead Regular Girl's family to treat her the way they do.
I think you have a good balance going of dialogue/exposition/narration! The introduction gave me a solid place to start without offloading too much information at once, and the conversation with the Demon didn't feel too lengthy.
The omniscient narrator was clear, but I agree with Naomi that it was especially hammered home when I got to make a choice for the Demon. It was unexpected - but really interesting! - and maybe a little bit of clearer lead-up to it would be helpful. Since this is an adaptation of a fairy tale, I think it's effective and a rather strong way to have the player experience the story.
The choices felt like they were giving me an interesting variety of ways to respond to the situation, and they gave me a pretty clear sense of Regular Girl's personality.
I really enjoyed playing this through! It makes me want to know what Regular Girl will do -- if she'll actually go through with the Demon's request, or if she'll ignore it and have to face consequences. I'm excited to play the final version :D