Here's a picture of my Black Australops at around 12+ weeks of age. As you can see they are pretty tall in stature and have long grey legs. They are quite docile and didn't fair well with my established flock of Rhode Island reds.
This is one of my Black Stars at 20 weeks, beautiful...
You may want to compare your black hen to the following breeds: black star, black australorp and a black copper marans. I had black australorp about 5 years ago and just remember them being black. I currently have black stars (a couple totally black, while others have copper around their head...