It is obvious that Calpurnia is more than just the housekeeper of the Finch family. As the only adult female presence in the household, she also serves as the mother figure for the two children. Scout has already explained that she always lost her battles with Calpurnia since Atticus was always on her side. So, when Scout scolds Walter for putting molasses on all of his food, Calpurnia is quick to caution her and then remove her from the table. Cal quietly lectures Scout on behavior toward household guests, explaining that no matter who the person is, if they are in the Finch home, they are to be treated with respect.
The scene shows that Cal has free rein over disciplining the children since she did not ask Atticus first when she led Scout from the dining room. This is probably quite unusual in Maycomb; few African-Americans are in a position to give orders to a white person--be they children or not. But Cal has Atticus' confidence and respect, and this unusual arrangement will continue in spite of Scout's protests.
In Chapter 3, Scout makes several rude comments about Walter Cunningham Jr.'s eating habits after he pours syrup all over his meal. Atticus shakes his head towards Scout before Calpurnia requests her presence in the kitchen. When Scout follows Calpurnia into the kitchen, Cal proceeds to chastise Scout for her behavior. Cal wastes no time explaining to Scout that her behavior was disrespectful and impolite. Cal even threatens to send Scout to eat the remainder of her meal in the kitchen if she continues to act rudely towards Walter. Atticus gives Cal permission to discipline his children, which is significant given the attitudes towards race in the novel's setting. Atticus views Cal as a member of the family, and she is clearly an authority figure throughout the Finch household. Atticus and his children respect Calpurnia, and she has a substantial amount of authority in their home.