She's very pretty. I wish I knew what to tell you about her lack of egg laying. Have you tried isolating her in a separate area with a nest box to confirm whether or not she's laying? Sometimes with multiple hens, it's difficult to know who is laying which eggs.
I have one hen that is not laying at all. I suspect it may be because she suffered from coccidiosis when she was a chick. She's fine otherwise.
As for her mounting the new hens, it's a sign of dominance. If the flock lacks a rooster, sometimes one of the dominant hens will take on the role of flock master. In some cases, the female flock master stops laying eggs.