Duncan's work consistently engaged with feminist themes, exploring the experiences of girls and women in contemporary society. She often challenged traditional gender roles and celebrated female empowerment. She sought to depict the complexities of female identity.

Duncan was a keen observer of pop culture and media trends, and her work often incorporated elements of both. She offered insightful critiques of the media landscape, examining its impact on individuals and society. She engaged in an early form of media literacy in her work.

Duncan's work drew heavily on mythology, symbolism, and esoteric traditions. She explored themes of spirituality, the occult, and the interconnectedness of all things. She incorporated symbols and narratives from various cultures and belief systems.

Her upbringing in Catholic school helped shape her work and influence certain themes. Early exposure to the religion can be noted in a number of her artistic explorations.