Colonel Tia Karim was a traitorous UNIT officer.
To reach her goal, she acted as a representative chosen to inform Sarah Jane Smith of the death of the Eleventh Doctor. Once she agreed to come to the funeral, along with Rani Chandra and Clyde Langer, Tia showed them around the UNIT base. She locked Rani, Clyde and Jo Jones' grandson Santiago in a wing of the base, and attempted to literally roast them by trapping them in the air conditioning and turning the heat up to maximum. She was aware the Doctor would save them, allowing the Shansheeth to capture Sarah Jane and Jo.
Sarah Jane and Jo were attached to a memory weave, but it overloaded as it was unable to compute all their many memories. When the memory weave self-destructed, Tia was caught in the blast and killed. (TV: Death of the Doctor)