Glad she is doing better!You're right, it was the gizzard full of stones, which would have been normal. I guess there could have been microscopic lesions, but there weren't any massively disturbing ones like the pictures online.
Anyway, Cocoa is doing better today. She's eating and drinking on her own again and not lethargic any more. I only tried the bread for one day, amd she didnt eat much of it. Today she has chick starter/grower and some scrambled egg. She still has very loose stool though. Should I wait for normal stools before attempting to put her back with the other girls? She's on day 3 of Corid, along with the rest of the flock. It looks like I should do at least 5 days?

Hope she continues to improve.
I also would go ahead and put her back. If she has been completely out of sight then I would make sure the pecking order return doesn't become too brutal. That depends on your flock.