I'd say that the platy is just trying to make sure everyone knows that she's the Alpha. Make sure that she isn't hurting/nipping the other fish. If she isn't, I'd say just leave them be, as there isn't really anything that you can do. If she is hurting them, I think you should get her a new home.
LOL! That's probably why she's beating up on him, he keeps pestering her! I had a female like that. She was always picking on the other platies, and also always pregnant and giving birth. I finally had to rehome her due to her aggression, but I still have three generations of her young.