She Had To Believe It Was
Juliet hadn't put much thought into other types of mages despite listing varieties of magic in her book. The only magic that made it into the story was water, fire, wind, darkness, and plants. Ice, stone, and light were left out.
Magic did come from bloodlines within the framework of this world so it made sense that Alec had learned from one of his parents. Ciara had as well but Krae had a variety of relatives to learn from. Ira pretty much had to teach himself since his mother died so early in his life.
Rukelion had learned from his brother since his father was too busy running the kingdom. His family members had been mentioned frequently during the prequel she wrote because they were his primary motivation to destroy Mirea.
Family was important to people. Juliet didn't know anything about Daisy's before she came to this world but now all she had was the villain and his unborn child. And Juliet was about to take away half of it.