@Introvert But why do i think she is the real daughter and swan is her mother in child form protecting her daughter from bad people 
as you can also notice her eyes similar to the duke and hair almost similar to the duchess exact opposite of swan black( hair of duke and blue eyes of duchess) concerning right
as you can also notice her eyes similar to the duke and hair almost similar to the duchess exact opposite of swan black( hair of duke and blue eyes of duchess) concerning right