Why does Molly keep talking about the fur coat in "The Fur Coat"?

In the short story "The Fur Coat" by Sean O'Faolain, an Irish writer whose original name was John Francis Whelan, a man called Paddy Maguire receives an appointment to government office, and his wife asks him for a fur coat. He agrees immediately, and then the rest of the story consists mainly of a conversation between them about the reasons for buying a fur coat.
What seems to be a very simple plot is, in fact, a subtle and sophisticated means of uncovering the true personalities and desires of the characters. Molly's first argument in favor of the coat is that it will enable her to look good when she attends parties and receptions. She reasons that she can wear just about anything if she has a fur coat on top of it. Paddy's motivations are more practical: he figures that a fur coat will keep Molly warm. It's obvious that he sincerely loves Molly, and he wants to see her comfortable and happy.
Molly keeps talking about the fur coat because she's not sure of her own motivation for wanting it. When she hears that they'll finally have some money to spend, a desire for a fur coat is her first impulse because they have been denied such things for so long. Later, as she is mending the children's pajamas, she discerns that the couple may have other more urgent needs that have to come first. When she realizes that the fur coat may not be practical, she reacts emotionally, and she and Paddy get into an argument.
In the end, Paddy and Molly make up. It's touching to see them resolve their disagreement even without solving the issue of the fur coat. The fur coat is ultimately symbolic of their change of status, and that's why Molly keeps coming back to it in conversation. The fact that they are unable to resolve this dilemma demonstrates that it will take time for the couple to adjust to their new, more prosperous lifestyle.