Adding more females MAY help the aggresion of the more dominant one. However, there are many times where the aggressive female will kill other females. I have also heard of situations where all seems well at first, but later one ends up dead. So, I can only tell you that if you do add more females, watch them very carefully and be prepared to seperate them if needed. Bettas (males or females) really aren't your traditional compatible fish. You might actuallly do better by just leaving one in the 10 gal. and giving the other one a 1 gal bowl. (If you do this, you might want to put the more aggresive female in the small bowl and let the other one mingle with your other fish.) Sorry, there really isn't an easy answer to this question. It just depends on how aggresive your dominant female is.