She seemed in a daze.

I thought Ronan did a great job. For example, after her character had dinner at Tony's house, and is a bit put off by his talking about their future kids, we then see her leaving night school. She walks out, expecting to see Tony, doesn't see him where she expects him, and scans the sidewalk and looks around. We then see her clearly disappointed expression. Not just disappointed, sad. She walks off, deflated. Then he calls her name. She turns and her expression brightens. A bit after that she very earnestly tells him she loves him too, but also firmly tells him not to put on the pressure when it comes to kids.

The two of them also share a sense of humor and like to snark at each other - we can see it in their expressions when they speak together.

She is kind of blank at home in Ireland, but I think that's a choice. She's passive at home. Then she's livelier with her friend Nancy, and then passive when with her mother. I think she feels guilty and at a loss. She has no job, no way of getting one, and any late teen-age girl would lack some confidence with a sister who is accomplished, and does everything for you, and there's no way of your improving your own lot.

Also, that mother (brilliant performance by the actress) - is presented as this oppressive presence - that once you're in her presence, the overwhelming guilt will suck you in and overpower your will. That was especially clear when Eilis returned to Ireland. I thought Ronan made one very good choice. It was the first time one of the villagers hinted at marriage to Jim (not the one who trilled "Jim and Eilis, Eilis and Jim, but someone even earlier) - you can see Eilis's eyes go blank. A wall goes up, like she's pretending she can't hear or understand what the woman is on about.

Correction: "emoting" all too often is part of overacting.