Awww poor little guy. I had this problem too, a few years back. After taking in a rescue that went unclaimed and then unwanted by the person who found her, I ended up with a somewhat aggressive hen. Shortly after getting a cute little boy that was supposed to be our ONLY bird.
I kept them separate for the standard quarantine time and then started to let them get to know each other from their respective cages.
Long story is she decided she was the boss and after several tries I decided that they would have to stay in separate cages. All the while poor boy just wanted to be with her sooooo bad and wouldn't do much besides cling to the side of his cage trying to get to her.
I went back and forth a few times over the years trying now and then to let them be together (they do appreciate each others company) but I didn't trust her to not be mean when I wasn't around supervising out of cage time.
Sorry for going on and on but I wanted to leave you with a little glimmer of hope... that she may mellow out with time (years) I highly doubt it and sounds like they will have to stay in their own cages but thought you may like to hear that you're not alone.
Several weeks ago I let them be in the same cage.
He was so pathetic trying, crying and chewing at the bars of his cage to get to her that I gave it another try...
NOTE: I am most always at home due to a disability and keep them in my bed room next to me for my own sanity, as well to keep a close eye on my little friends. My hen is still the dominate bird but has accepted him and lets him preen her and feed her but that's the limit. She will chase him off if he's trying to get a treat from me or if he gets too close to HER food dish. But for now its working. I always keep a second cage ready just in case I have to go back to the old arrangement, though.
I didn't ever expect to be able to let them be with each other even a couple years ago but time can change things I guess.
I don't recommend letting them stay in the same cage at all, at this time! And with your girl already attacking it may never be an option just wanted to share that I can relate to your situation. Good luck.