Originally Posted by KainRacure
Something like this happened in the winter of 2008 when she saw a cat outside.
Note I know conventional reasoning said she needs to be PTS...
Welcome to CatForum and I hope we can help you with your kitty.
You don't know it, but you've answered your question about what is wrong with your kitty and I don't think the problem is severe enough to warrant having her PTS. What she experienced in 2008 by seeing the cat outside, and what you just recently experienced, is feline redirected aggression. This is a response the cat has to a sight, sound or smell that triggers this behavior. They are acting instinctually and really cannot help it, other than trying to eliminate the triggers so it doesn't happen. You can use some products like a pheromone 'calming odor' in the form of a Feliway plug-in, it looks/works like an air-freshener but the odor/pheromone tells the cat "all-is-cool, be-mellow". You can also use other natural things, like Composure Liquid or Rescue Remedy to help keep her calm.
You could take her to a vet for an exam, but short of extreme ailments like seizures and/or brain tumors, I think the problem is going to be redirected aggression.
The cat sees, hears, smells something that activates its' instinct for survival (fight/flight), but if she cannot reach the source of this trigger, she "redirects" it onto those around her; other pets and her people. The best way to handle a cat in the throes of a redirected aggression incident is to handle it as little as possible and/or try to get it into a small room to hang out and calm down by itself.
Maybe someone else will be able to give you better advice. I've only experienced it once or twice, but neither episode was as bad as what you described. I *was* attacked by a new cat when he smelled the outdoor tomcat on my hands. He yowled and leapt at me, I turned my face and upper body and he just scratched my shoulder badly. He did that because I smelled like a rival tomcat.
Best of luck,
Redirected Aggression article from LBC: http://www.littlebigcat.com/index.php?a ... acasestudy