"Mirabel saw a change come over Mama. She saw it in the way Mama smiled, in the way she held her chin, the way her eyes filled with light. It was as though she was truly seeing herself for the first time. The dress seemed to bring out an innate beauty that had been hidden under layers of self-loathing. It was as if the two parts of herself, Dan Dan and Ai Ling, had stopped their fighting, had become one. The dress seemed to bring forth the combined beauty of both the girls' souls."
This paragraph shows that Mirabel really made her dress with different people's soul and innate beauty. She did not made the dress for her personal appreciation, but more like making dresses really fitting for people.