Grace has an inherent sense of romanticism.
Grace loves to dress up and pretend to get married and live happily ever after.
A sweet neighbor gave Grace this dress a while back. And Grace loves to wear it with her makeshift veil.
She dances and curtsies in it and pretends to go to grand balls with handsome princes. She even speaks like a princess by using a high pitched falsetto tone. Put a fancy dress on Grace and she transports herself to a wondrous imaginary and magical world.
Put that same dress on her sister and you get a slightly different reaction. Faith is more of a realist.