Cat on cat aggression, help?!?

I would venture that part of the problem is the fact she is not spayed. talk to your vet ( or get other vet opinions) about possible newer anesthesias. Not just to make her a happier girl, but to solve the agony of constantly going into heat, but that unspayed female cats (also unneutered males) have a HIGH rate of cancers of the reproductive organs, which includes breast cancer as well as uterine, in a cat. It is fatal as we usually dont know the cat has it until it has spread throughout the system and there is no hope but to end the suffering and euthanize. ANOTHER bad thing is the HIGH risk of PYOMETRA. do an internet search. THIS you WILL know she has. SHe will be very very sick and could even die before you can get her to a vet. If she does nt. the treatment is massive doses of antibiotic usually oral and iv, hospitalization and immediate spay needed (it is a virulent uterine infection ) that runs rampant thru the system... only now the spay is really life threatening as the cat is sick. some make it, many do not...and $$$$$$ at the vets as well as the suffering... SO I cannot tell you what to do, she is your cat... but I would get another opinion on the spay,. Just make sure they do not hurt one another. Keep the boy in a separate room . Look online for tips on "introducing a new cat into a home with a cat".. good luck..and thank you for for love and care of cats...Blessings to all..