This happens a lot with females, I am sorry you are going through this, if you had spayed them before they had their first heat things might have been different, but then again you never know. 2 alpha bitches in one house can be deadly, you may have to rehome one, I hate that for you, but one could kill the other. I had the same problem after one of my girls went into heat, but the one she was picking on is the alpha of the bunch(she things so) and put her in her place so I havent had anymore problems.(knock on wood) If I still did I would rehome the one cause the most problems. Good luck, I know this is hard for you.
Sometimes doing what you think is the worse thing(rehoming) may be the best for them.