Katje The Windmill Cat by Gretchen Woelfle illustrated by Nicola Bayley

Nico the miller treats Katje like a queen.  She rules the mill and Nico's house.  Then Nico marries and Katje feels displaced (especially when the baby arrives!).  When the dike breaks in the Dutch village, Katje earns her place again in the home because of her bravery.
Inspired by a true story.
Lovely illustrations.
-Borrowed from the library.