What would have happened if Eveline had gone away with Frank to his country?
James Joyce is clever in how he writes "Eveline," as he makes it appear that leaving to "Buenos Ayres" with Frank would be the heroic thing to do. However, as in all the stories in Dubliners, the answer is not that easy. Joyce suggests that if Eveline leaves her father and the other children she has to take care of in Dublin, she would move to a foreign country where she doesn't speak the language, doesn't have family, and would basically do the same thing (take care of a house, work, take care of children, etc.). Either way, Eveline would be ensnared by a sense of duty.
While Eveline found Frank exciting as "He had tales of distant countries. [...] He had sailed through the Straits of Magellan and he told her stories of the terrible Patagonias," she also felt duty-bound to her family. She even heard her dead mother speaking Gaelic to her, "Derevaun Seraun," which roughly translates to "The end of pleasure is pain." If Eveline had left with Frank, she would likely have fallen into the same habit of being completely duty-bound to her family.
However, there is a much darker way to look at what might have happened to Eveline: she might have been sold into prostitution. There is no mention of what Frank is doing in South America other than the narrator saying, "He had fallen on his feet in Buenos Ayres." What could this mean? In the early 20th Century, sex trafficking to Buenos Aires was rampant. Sailors would lure women away from countries like Ireland and take them to countries like Argentina (see attached journal essay).
Either way, it's likely Eveline's life would have been no better, and perhaps worse, had she decided to move to Argentina with Frank. Perhaps her duty to her family saves her from suffering a much more tragic story.