Interestingly, I don't think that this novel actually gives us an easy symbolic setting in terms of a divide between the country and the city. Rather, when we focus on the setting in this excellent novel, we need to focus on the different houses that Edna lives in or stays in briefly and how they act as markers of her progress and self-development. For example, consider the Chênière Caminada, to which Edna and Robert escape to. There, Edna finds herself in a world of romance where she has managed to entirely escape her social roles of wife and mother that are such an anathema to her. Coinsider what Edna says when she wakes up:
"How many years have I slept?" she inquired. "The whole island seems changed. A new race of beings must have sprung up, leavin gonly you and me as past relics. How many ages ago did Madame Antoine and Tonie die? and when did our people from Grand Isle disappear from the earth?"
Being isolated from her social roles, Edna is left free to construct her own reality and her own escape.
This is something that we see again in the "pigeon house" to which Edna moves. Note that she says her reason for leaving her family home is that "it never seemed like mine," and she can leave behind the elaborate gilded cage that Leonce had constructed for her. The pigeon house allows her to live her life as she wants, but at the same time it does not entirely give her the freedom that she completely desires. The way in which it was originally used to keep domesticated pigeons hardly bodes well for Edna's chances of gaining her liberty through living there. Instead, Edna realises that she does not fit in to any location, and that only in death can she find the true release that she is after.
Thus, instead of exploring a dichotomy between the country and the city, you need to think about the various locations in which Edna stays and how they comment upon her development and her search for freedom.