Dr. Peach did not originate from fanon, and the information on this page may not be entirely accurate to their canon. You may read more about this subject in the context of their canon on the following wiki(s):
Prior to Dr. Mario World, Dr. Peach was depicted as wearing a pink lab coat, with a matching hat and shoes. In Dr. Mario World, she wears a pink lab coat with a white undershirt and hot pink dress, as well as wearing white shoes and a stethoscope around her neck.
Dr. Peach appears in Dr. Mario: Flu Season as a player character unlocked after beating the 20th level of "Rush Mode". In Dr. Peach's mode, everything has been intensified by 100 percent and it introduces the ultimate megavitamin.