ok... I'm going to add something to my post....
I would never reccomend letting them work it out if you have an agressive dog.
I just don't want anyone thinking that I am for letting dogs fight it out! Thats not the answer... But 90% of the "fighting" that goes on is not really fighting at all... Its just a battle for position... And nobody gets hurt...
If they are actually attacking!!! Then Yikes... Its a problem! But it really sounds like your gal is just pissed and trying to let them know how its gonna work in "her" home!