The created AI persona represented two opposing aspects of Zhe's psyche and served as a physical manifestation of Zhe's self-doubt. Soon after its creation, it split into two separate, binary aspects, each as powerful as Zhe and drawing their strength and characteristics directly from Zhe.
They could change their appearance at will but ordinarily presented themselves as a boy and a girl. The apprentice was suspicious of all visitors, jealously guarding its exclusive access to Zhe, whom it called its originator.
When Zhe went into a voluntary stasis to drain them of power they took control of Zhe's private retreat for almost hundred years. When the Tenth Doctor and Gabby Gonzalez tried to visit Zhe, the apprentice assumed they were trying to get an apprenticeship and attacked them. However, the girl apprentice warmed up to Gabby and gave her a connection to the quantum sphere, enabling Gabby some very limited use of Block Transfer Computation. Eventually, awoken from the stasis by the Doctor, Zhe returned both aspects of the apprentice back into the quantum sphere, announcing that the experiment was over.
In the end, Zhe considered the creation of the binary apprentice a mistake and thanked the Doctor for helping her correct it. However, when asked by Gabby, Zhe did not exclude mending and educating it in the future. (COMIC: The Arts in Space)