I think she has been eating and drinking. She's not in the nest all the time and does go outside, so I assume she also eats and drinks. I'll keep an eye on her. At this point she's broody like every other day.
My 1 year old frizzle cochin has been loosing feathers on her neck recently. She was broody somewhat recently and plucked all the feathers on her underside, but I don't think that has anything to do with her losing them on her neck. I had an issue with a hen plucking a different hen last year...