Update: I swapped the ceramic eggs out for real ones yesterday evening, while mama hen went out (unwillingly--I really had to lift her off the nest) to do her business. When she went back into the nest box, she was clucking softly. Eyed the eggs really closely for a few tense seconds (remember, I've never done this before, so I'm sitting there like, "DOES SHE KNOW? IS SHE GONNA EAT THEM?"), then softly rolled them under her breast with her beak. Hooray!
Went out this morning and she's sitting on them, all fluffed up, and absolutely doesn't want to leave the nest even when I leave it open. Fingers crossed! She and I are both first-time hatchers, so hopefully between us we can figure it out.