When Albion Defence, a competing anti-alien organization, attempted to stage a series of attacks with telepathically-created monsters to create the impression that UNIT were incompetent so that they could take over Earth's anti-alien defence for themselves, Tara sacrificed her career to protect UNIT by appearing on a talk show and claiming that she was a member of Albion Defence to expose their crimes.
The Doctor concocted a plan to have himself arrested for Tara's murder. Tara herself was alive and well. Her part of the plan was to free the Doctor from his imprisonment in the Hesguard Institute. (COMIC: Sin-Eaters)