I agree with Justins1favmom

I cannot imagine that a 3 year-old does not even have a name... What do people say when they see her? 'Hi, little girl'? And what is on her birth certificate??
However, I would advise you not to call your daughter Cinderella. Just imagine for one second, you, yourself being called Cinderella? Would you like to be named after a fairytale princess?
I think everyone's suggestions were good though... You have many cute names to choose from; Ella, Ariel, Belle, Aurora... many things.