Oh and..... If a hen is to adopt it needs to be done when she has been sitting in the nest (broody) for around 18 days. The chicks need to be as young as possible so they will accept her as mom too. Even 5 days old can result in them not knowing to go to her for warmth.
A good broody mama will adopt hatchery chicks. Are they "hers"? They are once she accepts them.
That said....broody is the key. A hen that is not sitting will not adopt. Her hormones aren't set for it.