Predatory romance
Undine's story begins in medias res so to the reader, her marriage and the birth of her son seem good. But, before long, Undine reveals that secretly, she does not like marriage. She debates whether she is in the right relationship. This is tough because she is often in the wrong relationship on "accident." Over the course of the book, the reader gets an opportunity to see behind the veil of Undine's character to see if her predatory marriages are as "accidentally" broken as they seem. There is a chance Undine is intentionally using men for their money.
Money panic
There is no doubting Undine's desire for money. She is clearly motivated by a desirous lifestyle, and she doesn't have the character or commitment to make the kind of money for herself that she wants. Instead, she lives the lifestyle she wants and then suffers for that with money panic and unsurmountable stress. This stress is the suffering that makes Undine believe she is entitled to other people's money. Ironically, the men never have as much money as the let on, so she often ends up chronically paranoid.
Culture
Undine's life is rich in terms of her intelligence and social cosmopolitanism. She lives among bigwigs and powerful creators in New York City. She has a beautiful story of her moving from the Midwest to the Big City, to make a life for herself. Only one person knows that side of her, though—Moffat, her ex-husband. Her first experience of culture was spare and rural, so to her, the city is lavishly cultural and explosive in terms of stimulation. Undine is also high in her need for stimulation—she gets bored very quickly.
