The phrase "young witch" refers to a person, often a woman, who is still starting out or learning about witchcraft or magic. They are usually at a beginner or early stage in their magical journey. Full definition
Today's bookworms would never have met Hermione Granger - first described as having big teeth and bushy hair, then revealed to be the brainiest and most talented young witch at Hogwarts - without the miraculous creation of Jane Eyre. (layow.com)
And as she searches for an evil magic user targeting powerful young witches, she realizes that her only hope is to embrace her magical blood — or else she might be next. (goodereader.com)
And all of this is without mentioning Kiki's Delivery Service, Miyazaki's own film about a young witch and her cat. (slate.com)