Hen is crowing?

This is my silkie, Houdini. We moved into our current house pretty recently, and the owners had left her behind because they "couldn't catch" her. For a while we could only afford to keep her with two other hens, and she was very quiet the whole time. More recently, though, we bought three more hens. On the exact same day we introduced the new girls, Houdini suddenly started puffing herself up and crowing?

She hasn't been overly aggressive. Only pecks the other girls from time to time, then leaves them alone. Does this just mean that Houdini is at the top of the pecking order? Or is something else happening? We had chickens a few years ago, but we had a rooster back then, so he'd be the only one crowing. This is my first time hearing a hen crow.