I dont know about a posessive cat, but i know about a posessed cat. My cat ripped the shi* out of my arm the other day after it attacked my child. She's outside somewhere now. All i know is what i heard about birds. I heard that if a bird wont shut up you simply ignore it and as soon as it gets quiet, you pay it alot of attention. That way it knows the only way its going to get attention is if its not screaming. Im assuming the same would work for cats, children, etc... So next time, just keep moving away from the cat, or if you have to, put it in the room where its litter box is whenever it gets annoying when you have company. But if you have company and its being nice and polite, make sure you pat it for a few minutes. Like i said i know nothing about possesive cats, but its worth a try.