yay! Great news! I was never more interested in poop than when my daughter was in diapers. I wouldn't worry about the feathers growing back, although you will not have to wait for a molt for this to happen. I still think, and have read, that prolapse can be because of lack of calcium, or an overweight chicken may also prolapse. She may not have access to what she needs, so maybe think about a couple of places in the coop for them to get oyster shells.
We were very careful about returning Allison to a coop with complete day light, because we did it before and she prolapsed again. So we had her in reduced daylight for a month after she healed. There is healing going on inside that you can't see. And I do think we rushed to get her out the first time. If you can, keep her in as long as you are able. We actually ended up building a second coop for her and some other special needs chickens. Now she is happily laying almost an egg a day!
edited to add: we increased her daylight access gradually before putting her out all day.
