Sooo... she kept her black-ish nails. And ears.
Sorry, so not impressed. That's another character altogether, and we went from sorta-original-at-least-not-japanese-waifu to full-on japanese-waifu with goblin ears. In a non-isekai fantasy story.
@Allexio
It's explained in the wn i believe that she wanted to be both helpful and had a major crush on the MC, so the stone made her evolve into what she thought would be the perfect partner for the MC.