She was assigned by Georgi Selestru to go to Astronomar, which was in the path of the Dalek advance. Her job was to report back to Selestru anything she could learn about the Dalek conquest. She spent two years on Astronomar, fomenting rebellion against the Daleks, before being called back by Selestru.
She was surprised to be sent to Station Seven, orbiting Manikis, which had Dalek prisoners and a Dalek saucer. Sasha's job was to convince the Daleks to prevent the collapse of a nearby star. However, the Daleks tricked the humans, and Sasha, to save the station, sent the Dalek saucer, with herself in it, hurtling to Manikis' orbit, where it would burn up in the atmosphere. (PROSE: Mutually Assured Survival)