Once - Noor ho tebe - Miluju tebe
In reading the English Subtitles for the movie once I noticed that it lists her words as "Noor ho tebe". I researched this and apparently the subtitles are in error.
Even the actress has said herself that she says "Miluju tebe" meaning I love you. The characters played by Glen Hansard and Markéta Irglová are listed only as Guy and Girl.
Guy -- How do you say "Do you love him ?"
Girl -- Milujes ho ?
Guy -- Milujes ho ?
Girl -- Miluji tebe
I don't know Czech but I've seen her response as both "Miluju tebe" and "Miluji tebe". I'm assuming it's a verb conjugation difference.