I have noticed that their feed consumption increases quite a bit when they are laying over when they are not laying. Could be she is just eating more than the others because she is laying. Feel her breastbone to make sure it doesn't feel sharp.
I got some half starved birds from a guy a few months ago and he fed them scratch and their crops were softball size and very firm. I left them in a crate with just water the first day and their crops cleared quite a bit, still full, but at least the contents moved around some when I moved it with my fingers, gently. One cleared almost completely in two days, the other took almost four days to clear. I thought they were a lost cause when i first saw them they were so skinny and their crops were so hard. I thought they were impacted. After their crops cleared they ate like PIGS for about three weeks, pooped like meat birds and gained a lot of weight and found good homes. They were given to me because they "wouldn't lay" well no kidding! They were fed very pooor food, and not enough of it. Sorry, I'm ranting now... I'm sure your birds are not in the same boat. I just got to rambling there...