I see my clients on a one to one basis, however if they want to bring someone with them regardless of whether or not that person is doing the diet, fine.
Some CDC's hold group sessions, some don't. Some go out to houses, some don't. Its really up to the CDC. If you are not happy with any aspect of your dieting time, then discuss it with your CDC. If you want one to one you may have to ask. I always tell people on the initial contact that I work one to one.