The purpose of the machine is to take care of an infant. The robot's equipped with a lullaby, a whistling toy, a bottle of milk and a metal belt. She can also change a baby's diaper, and has the proper equipment and protocol to do so. She also has a calm, soothing voice.
The Robot Nurse Maid cannot define if one is or is not a baby, and therefor mistakes Donald Duck for an infant and treats him like one. And when the Nurse Maid gives milk, it takes a bottle and slams the bottom of it, spraying the baby with milk.