If the Iams is working for her, there is no need to switch brands, just switch to the adult formula when she is about a year old. You wouldn't want to keep her on the kitten food once she's mature to prevent her from gaining too much weight. When it's time to graduate to adult food, mix one part new food to three parts old food, then half and half, then 3 parts new food to one part old food. That will get her taste buds and her tummy used to the change.