Père Goriot's daughters are best analyzed together, for both of them are the result of an over-permissive and blind love and of a money-corrupt society, the real unifying element of the book.
Brought up by a father who gave in to every one of their whims, who reared them as duchesses, they could not escape developing that self-centered egoism which we always find in them. But was not that upbringing itself also based on money, for Goriot gave them all that money could buy, including their husbands?
This leads us to Balzac's important idea of social preconditioning; they adapted readily to the social mores that acknowledged the fact that most girls married for wealth and prestige rather than for love and that, consequently, they had to lavish their passion upon someone other than their husbands. This triangular relationship is the source of the most dramatic psychological imbalance found in the two women and is quite apparent and often repeated in Balzac's works in general and in Le Père Goriot in particular.
Bound to their lovers, who also were hunting for money and prestige, they had to give away their money as well as their dignity as women. This explains Mme. de Restaud's paying for her lover's debts. This explains Delphine's lowering herself to ask Eugene, almost a stranger, to gamble for her to repay her former lover, De Marsay.
In both of them, there is exhibited a slow rotting away of their moral values. There is, however, a distinction between the two females.
In Anastasie, we find the cold, calculating egoism of a woman who has been consciously bleeding her father and ostracizing him at the same time and whom Balzac punishes greatly for it, as she will see her fortune and her children taken away from her and will have to come back to her father to humiliate herself in the last part. In the end, she has lost everything, even her father, but we don't doubt that she will continue, as preconditioned, to put up a front to the world.
Delphine also displays that egoism, but it is presented to us as brought on by passion, and, in her outbursts of emotion, Delphine shows herself so naive that we cannot deny feeling compassion for her. True, she used Eugène at first to be launched into high society, but she later shows such a true love for Eugène that we can't help liking her even when, by accepting Rastignac's love, she is rejecting everything else — family and father: "All my life is in you. My father gave me a heart, but you have taught it to beat. The whole world may condemn me. What does it matter if I stand acquitted in your eyes?" It is really affecting to see genuine emotion stifled by social mores.
And we know that Delphine is hardly going to change. She will be the same selfish, but likable, character that we find so often in a social environment where "fortune is virtue."