My duck, Thimbleberry, had something similar happen to her about 3 years ago, but I think not as serious. I went to pick her up one evening and I felt something hard on her bottom. I couldn't tell what it was. It was almost as big as an egg and looked like it had some shell material but also something dark and was attached to something inside her. She was trying to push it out and was prolapsing.
Luckily we do have a 24/7 emergency avian hospital, so I called them and they told me to bring her in ASAP. They did emergency surgery at 11pm and I left her there overnight. They also tube fed her, gave her fluids, and antibiotic and vitamin injections. I brought her home the next day and kept her inside away from her flock for two weeks. She also had to take antibiotics at home. The mass was attached to Thimble's reproductive system, but her intestines were fine so we didn't have any dietary recommendations aside from make sure she eats.
I hope Daisy recovers well. Keep us updated.