Three cases where Christine de Pizan seems to have transformed her sources are discussed. The first involves a fusion of the Tiburtine and Cumean sibyls, the second Christine's treatment of the poetic muses, and the third the image of felicité humaine introduced at the beginning of Le Livre du corps de policie. It is argued that where Christine transforms her sources she is making a distinct philosophical point. In the third of these transformations she shows a subtle appreciation of the sexism of a traditional philosophical metaphor, which she cleverly undermines and subverts.