Who is Clarissa Montgomery and Holly Grace from Francie and what is their importance?

Clarissa Montgomery is the niece of Mrs. Montgomery who employes Francie and her mother for household work. The Montgomery home is beautiful, as is Clarissa's room, and Francie tries to imagine what it would be like to live there. Although Clarissa is a member of the group that has treated Francie poorly, she shows an interest in Francie and gives her a book. Later, when Prez and Perry are hiding near the Montgomery gazebo, Clarissa drives the boys home to Three Notch without her uncle's knowledge. She seems to enjoy the family atmosphere in Francie's humble home. She gives Francie a book to give to Jesse Pruitt, and later returns Francie's Nancy Drew book to her that was confiscated at Diller's. She is the kindest white person in the story.