Marietta was born in Tarrytown, New York. She spent most of her childhood making mud pies, swinging on rope swings, dancing, and recreating her grandmother’s paintings.

She moved to Boston to earn her degree in Illustration from The Art Institute of Boston (now Lesley University College of Art and Design), where she spent a considerable amount of time sketching at the Museum of Fine Arts, writing random essays in her notebook, and searching for the best cannoli. She creates all of her illustrations using multiple media, including watercolor, color pencil, graphite, ink, and sometimes tea (accidentally).