As you know cats are vicious, evil little monsters - you have your work cut out.
This site usually gives good information
http://www.fabcats.org/behaviour/index.php and hopefully you will get some ideas of how to make your home less like a war zone.
I have two siblings - I thought that they would be best friends and curl up together. They alternate between hating each other to ignoring each other - no matter what we, mere humans, do we always fail to please our masters.
Failing all the usual stuff you could try getting Izzie hooked on catnip, maybe she will turn into a mellow kittie. On the other hand she could turn into a psychotic killer. Cats!!