Who is Piper Williams from Al Capone Does My Shirts and what is their importance?

Piper Williams is the warden's daughter. Piper is a strong, determined young woman who is always coming up with schemes to use her home on Alcatraz to her advantage. Piper comes up with a scheme to sell laundry services by Al Capone to the kids at school, resulting in punishment not only for herself, but for four of the other children on the island. Moose is fascinated by Piper, but at the same time he dislikes her because Piper is beautiful and she has a mind of her own. Piper proves to be a problem for Moose in more ways than one.