My hen is sick! I'm worried.....?

So my Australorp hen is sitting in her nesting box, as she has for the last 3 days. She is at the topof the pecking order, so usually she is the one who gets all the food. She hasn't been eating anything, and she won't move. She just seems so drained of energy. I've placed bread and scrambled eggs right next to her, along with a bowl of water, but she's not eating/drinking. I know she isn't egg-bound because she layed an egg a few hours ago. What could be wrong?? Thanks in advance.