I have no idea what the answer to goadra/Barbara's is, so I'll answer Amanda's instead:
Jack is dancing with Lureen and changes his demeanor when he hears the song lyric about being lonely.
Ennis's face changes when Alma talks about him growing up so lonely?
I just wanted to post one, because I finally thought of one:
Jack comments on how much Ennis has spoken.
(This one is probably a mirror, if I understand the definition.)