I have 5 cats right now. Have had as many as 7. The easiest to introduce to my older and aloof cats were the kittens. Another older cat with a well established personality is harder. No matter what Taffy may never really be friends with another cat. But what you are looking for is another cat that can hold it's own but also doesn't really NEED the other cat to like her. So I recommend younger is better.

K