Hello Jen, I dont know if you have been welcome, but here it goes... Welcome to RF. I hope I can help you with your questions. If I cant then I will help you bug the experts here to answer your questions.
When you bought them? are they like babies? and now they are grown ups? Pay attention to what happen next, If you think that the small ones cannot defend himself the try to remove it. But in my experience specially if they are juveniles and the same size. They dont know yet whose going to be male or female. Now that we know in your case the bully is the female, and the smaller one is the male, then they will still need adjustments since they are also new to this relationship deal. The other fish says, Im the boss, and the other says, no I want to be the boss. Later down the road, they will realize who will become the boss and they will be at peace.
I forgot to ask... are they the same species? the same kind of clown?