In 2005, she graduated from the School of Visual Arts. Her first self-written and self-illustrated book, ''Melvin and the Boy'', was published in 2011. In 2012, her work was exhibited at the Bruce Museum in their "Let It Snow! Children’s Book Art" show. In 2020, Castillo's book ''Our Friend Hedgehog: The Story of Us'' was published, which is planned as the first book in a series.