In the scene where it's discovered Edwina hasn't laid any eggs, Ginger whispers to Bunty, "Why didn't you give her some of yours?" Bunty replies, "I would have, but she didn't tell me. She didn't tell anybody." Since going a week without laying eggs lands a chicken on the chopping block at the Tweedy's farm, which has already been established as a pretty rotten place to be, Edwina effectively committed suicide.
Either that, or she became essentially a martyr. Seeing an usually productive hen such as Bunty lay less eggs than usual could have been taken as a sign that she wouldn't have been worth keeping within some weeks.And that could be said of any other chicken.Edwina simply preferred to accept her fate rather than risk having someone else be unjustly killed because of her.
The main page doesn't omit the fact that Tweedy's Farm is a Crapsack World. Real chickens in factory farming have it much, much worse. At least these chickens can go outside.