I'd freak out at prolapse as well, totally understandable freak out! But even after you'd been to the vet a couple times, it felt to me as I was reading along that you didn't trust your own judgement and/or needed to ask your vet more questions, but instead were perhaps relying too heavily on BYC for input. Invisible chicken friends can be very helpful (and most certainly have been in this case), but only you and your vet who have actually seen the chicken and really know her can make the final decisions. It felt like you were afraid to make move or decision on your own, and you need to get to a place where you feel confident to do so.
You are doing great, and Rosey is living, breathing, clucking proof of that. Perhaps there is a thread here with good book recommendations, or maybe your vet could recommend one to you.