Help, rescued 6 featherless battery hens, they're recovering well, except one who is picked on, pecked and generally not refeathering- due to attack I think. Should she be isolated? For how long and at bedtime too?

Often in nature a weaker animal is disposed of to keep the "herd" or "flock" better though selective mating and elimiating any animal that has or is different.

Perhaps isolating them completely for their safety till they are much much larger and older.

Hi.
If the other chickens have pecked her until there is blood--they will eventually kill her--it's a means of keeping the flock safe by not having the smell of blood around. I've seen in young chicks as well. Isolate her for now until she gains some strength. Reintroducing her to the flock might be hard and she will take a beating while the new "pecking order" is established--but if she has regained her strength she can endure it. If you can put her in at night with the others and take her out at first light it might make reintroduction less difficult. Get some crushed oyster shells and put some out with their feed, and some vitamins that go in their water to make sure they have nutritionally the stuff they need to regrow their feathers. My birds loved the sweet feed that's made for horses--it has pellets and grains and molasses--full of healthy yumminess.
Good luck! Thank you for rescuing them! :D