Black Australorps and Orpingtons are in no way the same breed.
How many points on her comb? Most Black Australorps have five pointed single combs. They also have black/slate legs.. They are less fluffy, and have green and purple beetling on the feathers in the sun. They are calm birds and good layers.
Black Orpingtons are very rare in the US. They will be much fluffier than the Australorp. Hens have a very distinct, fluffy patch of feathers on their backs that looks like an old-fashioned lady's bustle. Their legs tend more towards slate than black.
I don't know what breed your hen is, though, sorry.
