She looks identical to Lucy one of my newest four EEs. If her legs and feet are a slate grey or greenish color instead of white or yellow, then she's an EE. (Easter-egger).
Note the extreme joy your chicks are displaying at finally being able to act like real chickens. This just isn't possible when chicks are confined to a small brooder indoors. I used to brood that way, too. Then I discovered outdoor brooding, and my chicks get to act like chickens from their very...