how ofetn do you take your cats to a vet doctor??

Unless the cat is very old or has a lot of health problems I don't see any need to take it to the vet every month. When my cat was a kitten he went a few times to the vet for his injections and to neuter him, but we don't expect to take him for at least another year - unless he suddenly falls ill of course.

We take our cats once a year unless they are sick and require additional attention.

Does your grandmas cat have health problems? If not she is taking it to the vet way too often. A healthy indoor cat really only needs to be taken in for a yearly exam, or when shots are due. Unless there is some other issue that needs attention.