You will know when shes gone broody because she just sits in the sleeping hutch for ages and she may lay a egg and stay on it for ages because she wants a baby but she cannot....
Also she will make noise before she lays too either find a nest or theres a predator and shes scaring it off just to...
I reckon she is getting ready to lay, Either Tonight or Tomorrow! She is making that noise because she wants to find a Nest and she cant just leave her too it and she will. Shes probaly going more red because the egg is getting closer to being layed, My chicken made alot of noise and she layed...