Throwing up, and lethargic hen! What to do? D:

For the last week My bantam hen as been acting 'not herself' She was eating and pooping fine, But she would just wonder around as if she was lost and making really weird 'cooing' noises almost like a pigeon! Then last night, When I was filling up her water and giving her new Grit, she threw up! I looked at it, it didn't seem really bad, just what looked like water and her food. she did this two more times, and I don't think she's done it again.
Now this morning her feathers around her face and beak are gone! And her crown and nose are really crusty looking, like dry skin, She's not sneezing she doesn't move from her nest box, but to eat and drink! And I know she is not broody since she hasn't started to lay yet, Or can hens be broody without laying eggs? I highly doubt it.
Right now she's inside away from the others. I don't know if it IS a cold or sickness that can carry between chickens, but I don't want to chance it. But it might be to late!