Much discussion has been had over the cat's role in Animal Farm by George Orwell. Some think she represented the wealthy, educated class because, like them, the cat did not work other than, perhaps, catching mice, for which she received benefits--milk and a home. The cat does not seem to have any real interest in Animalism and disappears whenever there is real work to be done. She is above manual labor.
Another possibility is that the cat represents the problems inherent in Communism. She is somewhat of a shady character, who tries to convince the birds to come closer, using Animalism as a reason she "cannot" harm them, though the reader gets the feeling that given the opportunity, she'll devour the birds in a heartbeat. She has not bought into the idea of Animalism, like so many people who did not buy into Communism. In order for it to work, everyone had to participate. The cat used Animalism to further her own life, but she never cared about any of the others.