Sometimes when you hold them and they struggle, it makes it worse. Stop trying to push it back in, but keep it moist. I would let her relax on a warm slightly moist towel. If you have a heating pad, you could put it under the moist towel and set it to LOW. That might help to lay the egg. Keep in mind that she may prolapse farther out, and that might require you to put her down. Did you give some calcium already? Calcium helps the muscle contractions to help pass the egg. Keep in mind that this is really a tough thing to treat, and you are doing a good job. Many people put chickens down who have prolapses, and in the past that was more common than trying to treat them.