I wouldn't cut back too much on her feed, unless you are a lot warmer than it is here in MI. Single digits here. Keeping her out of the light should work. If that doesn't work go to your vet and tell him you have a goose that needs badly not to lay eggs for a while, he should have something that will stop her, but it might mess her up for laying the rest of the year. If she does have a prolapse, use Preparation H, or in a pinch, sugar water to take down the swelling, and if it doesn't goo back by itself, gently push it back in. Skunks are famous for prolapsing, so I have dealt with that, but not in a fowl.