Madame Valmonde looks at the child in the best light possible so she can have a clear look at his skin. At this point, it is becoming clear that the child is of mixed heritage.
She focuses her look on Zandrine, who is looking out the window, for two reasons. First, she sees the child's coloring is becoming similar to Zandrine, who is a slave, and second, she wants to see if the nurse recognizes this fact.
Madame Valmonde is trying to protect her daughter from the truth.
