Sally was the inventor of the VSAI 001. In 1970, she received a message from the Eighth Doctor, which he sent to her in his future. The message notified Sally that the Doctor had funded the Institute one billion pounds. She created a time space portal in the Doctor's house in 107 Baker Street, where Daleks came through. She wanted to travel in the Doctor's TARDIS but she was killed by the Daleks as she tried to escape with him. (AUDIO: Fugitives) Molly O'Sullivan realised that Sally would now be alive since the timelines were negated after Straxus killed himself. (AUDIO: X and the Daleks)
After the timelines were negated, Sally was meant to die after being hit by a taxi. She was saved by the Master using the pseudonym "Harcourt De'ath". They then went for coffee together shortly after. (AUDIO: Time's Horizon)
The Master then used Sally to help him use the Eminence for his own ends. He taught her how to pilot his TARDIS during this time and gave her a Tissue Compression Eliminator. She locked The Doctor in a freezer and captured Liv Chenka, The Doctor's companion, who turned out to be the companion the Master didn't want her to kidnap, something he scolded her for. When the Doctor showed up to the Ides HQ and allowed the Eminence to gain control of the Master's TARDIS, Sally helped the Master to expel it into the Time Vortex. Shortly after, Sally helped the Master to kidnap Molly O'Sullivan. (AUDIO: Eyes of the Master)
Sally accompanied the Master and Molly into the Eminence war with humanity. There she helped the Master to inoculate humans with Molly's retro-genitor particles. She used the information on Heron's World to try and work out the dosage needed to inoculate people, taking into account their age and weight. (AUDIO: The Death of Hope)
She tried to negotiate with Jaldam to get the humans from Ramosa, where she unexpectedly encountered the Eighth Doctor. She wanted to see how her experiments had concluded. By this stage, she had programmed her ship with her voice. She helped The Master remove the humans from Ramosa via his TARDIS. (AUDIO: The Reviled)
Sally was sent to check on Markus Schriver, a scientist whose research would lead to the creation of The Eminence. She encounted Liv Chenka. who was there acting as Schriver's assistant. She ordered Schriver imprison Liv, which he did. Liv worked out why Sally programmed her voice into the computers, as it left an imprint of herself as she knew that she was expendable to the Master. Schriver became paranoid over what Sally and Liv were planning and killed her in a process of random selection between herself and Liv. The Master discovered her corpse and showed a brief moment of sadness before moving on with his plan. (AUDIO: Masterplan)
Sally was an incredibly talented scientist who was excited by The Doctor's presence and was eager to travel with him in his TARDIS. She was gunned down by a Dalek before she had the chance to, however.
In the second timeline where she was corrupted by the Master, she was cruel, cynical and cunning. She was nasty to everybody who wasn't the Master. She was smitten with The Master and obeyed his every command, even without the effect of hypnotism, something the Master valued greatly.
She was scared of dying and cried hysterically before her demise. This contrasted with Liv's calm approach to being selected for death.