I was in the same situation as you once, is just terrible to see them fight
Sadly my 2 girls never stopped once they started so I end it up rehoming both of them as they both were alpha types.
I was putting a gate after each other until they also started to fight thru the gates , they couldn't have eye contact ....they want it to killed each other. I was so sad over this, I though it would never happen between my girls , I heard about situations like this but you can never belived how bad they fight until you see it with your own eyes.
Now, the first thing that I ask about when bringing a new addition is about temperament, then I go from there.
Hopefully things will get better for you .......their safety now depends on you, don't ever trust them 100% , they can be friends one time , then hate each other right back. Good Luck.