Two speakers, two dialects, and pairs of lines that rhyme—this is a poem about doubleness and pairing, and the setting is no exception. As with all the stuff we just mentioned, there are also two settings.
Obviously, there's the town, where 'Melia and the other woman bump into each other. We aren't given a lot by way of description, but there are plenty of little hints. In this poem, the town is full of people like 'Melia, who dress in fine clothes (like "sweeping gowns" and nice gloves), look pretty, speak proper English, wear feathers, bracelets, makeup—all that kind of stuff. The town is just the kind of place where you'd be likely to run into these ladies.
The other place is where 'Melia used to live, and where the other woman still lives: rural England. It is a place full of farms (or "bartons"), where laborers like the other woman (and formerly 'Melia) wear "tatters" and work out in the fields, digging for potatoes and pulling out weeds ("spudding up docks"), getting all "blue and bleak" while their hands turn into paws (from blisters, perhaps). If the people in town speak a nice, proper form of English, the people in the country speak a stranger, less formal dialect. It is there that you'll hear words like "spudding" and "megrims," and people pronouncing "this one" as if it were "thik oon."
Stepping back for just a moment, you could say that the town symbolizes wealth, culture, and education, while the country symbolizes labor, dirt, grime, lack of education and all that. Ironically, even though the town is cleaner, it seems less pure. It is where you can find ruined women, women who have left behind their former lives and, ahem, compromised themselves. At the same time, the country ain't no walk in the park either. It is a place where one's body really takes a beating and where people are "ruined" in a different, social way.