I understand your problem
I have two boys myself
They're still very little but they do get rough sometimes
But you need to remember ... dogs are pack animals
and they always need to know where they fit in the hierarchy of things
Your girls are fighting for dominance
but constant fighting can be stopped if YOU have made yourself the Alpha dog
If one is constantly picking on the other YOU immediately go to the instigator and push her with two fingers and say NO!
Best to get her when she is stalking or when she is growling before they are at each other
My boys are just 10 weeks but I know that its coming
I already hear their play sometimes end with a high pitched squeal when somebody gets hurt
