Gold Comet with distended abdomen and trouble walking

I have a Gold Comet Hen and she has developed a large abdomen and it appears that everything has just dropped toward the ground. Her butt has gotten really wide and she waddles really bad when she walks. It has become so bad she can't step over a 2x4 in the chicken coop. She still eats and drinks and does have some have some feces on her tail feather but not a whole lot. She gets winded very easily when walking and I am just not sure what is going on with her. She is housed with 15 other hens in our coop and gets to free range occasionally. What could possibly be wrong with her? I am not sure she if she is laying eggs since she lays in the same place as the other chickens.