While I can understand how difficult it is to live with Ally I have to say that I feel irritated- to put it mildly- by someone who attributes to a cat characteristics like "nastiness" and "evil hatred".
I am absolutely convinced that I would attribute these words to very few humans in the world and definitely not to an animal. It is an anthropomorphism of the worst kind.
Frankly: if you feel overwhelmed by this poor cat that has been sent over the world like a parcel, has lost all her life several times and is like most cats not happy with living in a big group then bring her to a shelter- even if the risk is there that she may be euthanized. But do not take this b...s...(edited for cussing but still felt exactly that way) reading as a rationalization for it.
People who know me here for years will know that never in all my ten thousand posts I was using words like in that last phrase. I rather will not speak. But to kill Ally for her being evil- that is medieval! And if that should happen on this board while I just stand by I could no longer look in the mirror.