When you say she is listless, do you mean droopy and sad looking or just sitting quietly? If when she sits in the nest she is not laying, has her wings spread as if to cover eggs, and when you go to move her she raises her neck ruff to see you off, making the noises Cameron described, then she is broody - it's the time of year for it. If she is egg bound - well, I'm not sure but I think she would be in discomfort, squatting and with a heavy lower abdomen, sometimes with a mucky vent area. Soemone else will come along and tell you how to treat her if she is egg bound.