A running theme in the novel, one that Anne Elliot vigorously disputes, is that women are inconstant: it is what Wentworth believes about Anne for breaking off their engagement seven years ago. Much of the novel is about Wentworth becoming persuaded anew of the constancy of Anne's love.
Beyond that, and on a more general level, the novel continues Austen's critique of the limitations society places on a woman's possibilities. For example, as an unmarried woman, baronet's daughter, Anne, is undervalued and often invisible. She finds herself at the beck and call of a married sister who is a less mature and intelligent person but ironically has a higher status through marriage. Moreover, she achieved this status by marrying a man Anne turned down.
Anne, despite her commendable, steady, and appealing personal characteristics, has little agency because of her spinster status: for instance, she has to move to Bath, a place she dislikes, because of her father's decision to do so.
Other women are also constricted by their situation as women: for example, Anne's old school friend Mrs. Smith, a poor widow and invalid, is not in a position to reclaim the money she has been cheated of. Elizabeth, Anne's older sister, has to cope with the increasing anxiety of getting older without a marriage offer and with no other avenue of establishing the status she so badly craves.
However, in the marriage of down-to-earth and energetic Mrs. Croft to Admiral Croft, Austen models the kind of companionate relationship that Austen saw as an avenue to a fulfilling life for a woman. Mrs. Croft accompanies her husband on his sea voyages and projects a cheerful pragmatism.
Lady Russell, though a sensible mother figure to Anne and a preferable role model to Anne's snobbish father and older sister, nevertheless represents the woman in society who is too cautious and too carefully conformed to a culture that expects a woman to put security first in marriage. The younger Anne listens to her advice that she break off her engagement with Wentworth because his prospects are so uncertain but later comes to severely regret not letting her heart rule her head.
Overall, the novel examines the various problems facing women as they attempt to successfully navigate a restricted and yet high-stakes set of choices that will determine not only their financial future but also their happiness and human flourishing.