The Doctor took Milena for a trip as a favour to her father, the ruler of her homeworld of Xenon and an old friend of the Doctor's.
The trip went smoothly until the pair were forced to land on an asteroid, where Milena was possessed by a species known as the Zicons. The Doctor was able to expel the Zicons from her body and returned her to Xenon, with Milena having no memory of what had happened to her. (PROSE: Milena)
If a medium is not mentioned, then this incarnation did not have companions who were original to that medium; it does not mean that this Doctor failed to appear in that medium.