Your thesis for the story, "Eveline," from Joyce's Dubliners would depend on your interpretation of the story and the approach you want to take. I can suggest topics and research questions easier than I can write a thesis for you (especially without more information on what you have in mind).
Some possible topics include: isolation, responsibility vs. freedom, paralysis, the relation of "Eveline" to other stories in Dubliners, illusion and reality, emigration, and epiphany. This list is not exclusive.
Research questions might include:
- In what way is Eveline paralyzed?
- What is Eveline's motivation for staying?
- How does Eveline's isolation relate to the isolation of the protagonist in "Clay" or "A Painful Case"?
- Does Eveline in any way compare to Joyce himself, who lived much of his adult life away from Ireland?
- What is Eveline's epiphany, and does it come too late or too early?
These are just some ideas of what you could focus on. Answer a research question and that could be your thesis.