There are actually two Nanas in the novel: One is the simple girl of the streets who wants to be respected but does nothing to gain anyone's respect; the other is the symbolic Nana who represents the erotic love goddess and who embodies the concept of extreme sexuality.
The simple Nana is a girl from a disrupted home — her father died of alcoholism and her mother of starvation. She is the product of the gutters of Paris, and her environment influences her actions throughout the novel. She can never escape for long the environment from which she came. Regardless of how much luxury or elegance she is surrounded with, she periodically returns to the streets to pick up men at random merely to relieve her sense of boredom.
This Nana possesses no particularly outstanding traits. She has no wit, no talent, and no intellect. At times, she can respond spontaneously, as when she tries briefly to be true to Georges Hugon, or she can have a perverse sense of loyalty, as when she adheres to Fontan in spite of his brutality. But in general, she is a simple girl from the gutters of Paris who, by accident, possesses the most magnificent and lustful body of the age.
It is as the second Nana that she becomes famous. Her physical body is such that it excites and arouses the most basic and elemental lustful drives in the male. Sexuality emanates from her every pore and appeals to the animal instincts in the opposite sex. She brings about the corruption of love by appealing to the lower and more bestial instincts in men.
As a product of her environment, Nana has also adopted the values of that environment which are actually no values. During the course of the novel, Zola leaves no immorality uncommitted by Nana. She is incapable of being true to anyone, she constantly deceives everyone she associates with, she has no respect for any person or institution, she will sleep with anyone at any time, and most important, she drags everyone else down to her level. The interest in her character derives from the fact that she can at times be capricious, generous, hateful, spontaneous, and designing. She appreciates the power of her sexuality and uses it to its full advantage.
Finally, she represents the values of the particular age. When she spends money extravagantly, when she acts capriciously, and when she demands excessively from the men who adore her, she becomes a symbol of the age which sacrificed virtues to enjoyments.