This of course is the key question that we should be asking ourselves about this short story. You might find it interesting to know that this short story is part of a collection of short stories by James Joyce entitled Dubliners. Part of the thematic unity of this group of short stories lies in the way that Joyce presents the protagonists as being profoundly affected by a kind of paralysis that he sees dominating Dublin. They are unable to do anything for themselves, and seem, to a large extent, to be carried on along the tide of Dublin and to not have agency over their own lives.
I think we can definitely see this paralysis at work in Eveline. At the end of the penultimate section of this great story, her mother's memory inspires her to leave as she seeks to avoid a fate like hers. However, in the final section, we see Eveline struck by a state of paralysis. She seems unable to want to make the decision herself. She gives the decision to God to make for her rather than having to make it for herself:
She felt her cheek pale and cold and, out of a maze of distress, she prayed to God to direct her, to show her what was her duty.
This of course shows her inability to take charge of her own life, as she has to leave the decision to a higher authority. Lastly, when she refuses to go with Frank, she is described as "passive, like a helpless animal," clearly indicating the way that she lacks agency and the ability to determine the course of her own life.