Poor baby! Um... I know she's a friend and all, but my cat would come before her cat. She and/or her cat would have to go, personally. I mean, did she not know her cat was aggressive? His cats should not have to live in fear in their own home.
I've watched that TV show My Cat From Hell and dude can do some amazing things with crazy cats, but I really wouldn't know where to start. I hope someone else here has some advice because my only thought is someone's got to go.