The irony of attachment
As Robin seeks to become more attached to people, she finds herself wrapped up in weird moods, frustrated, and sometimes bothered by the drama of life. There is an irony about attachment, because she both wants and doesn't want intimacy, and also because she both succeeds and fails. Ultimately, the irony of attachment is her existential loneliness.
The irony of free love
To Robin, she is simply a romantic, a free lover. In reality, her relationships to sexual affairs are less innocent than she admits—or at least Nora feels regret about Robin's wayward eye. Nora's understanding is ironic, because Robin is just obeying her beliefs, but Nora expected something more intimate and personal. The free love comes at the cost of Nora's trust.
Break ups and distance
There is an irony present in the aftermath of Nora and Robin's affair. Neither can forget the other, so they are haunted by each other in their imaginations, because they can hear each other's voices, so to speak. Nora goes for therapy, and Felix returns to the comforting confines of his role as a father, but ultimately, Robin ends up harming a lot of people when she leaves, because her voice lingers in their minds.
The irony of religion
Here are a few ironic things to notice in the symbols of Robin's last scene. She finds a random church, unexpectedly, and it is decrepit, which is an ironic sign of its impermanence, ironic because of the permanent claims of the church of course, and then there is a dog, resting. The same dilemma that causes Robin anguish, the thought of a God orchestrating her reality, causes the dog to rest, a picture of nature at rest.
Anonymity and love
To Robin, sex starts to become a practiced demonstration of intimacy, rather than intimacy itself. She doesn't know many of her partners, and they don't really know her, and if it is an exchange, then it is a happy one, so Robin doesn't have to notice the negative aspects of her actions. By freeing herself from shame, she does come close to love, but there is no intimacy in pure anonymity except the thrill of sex. In the end, those love affairs end with loneliness, ironically.
