Sally Jacobs was a UNIT secretary (TV: The Christmas Invasion) and Systems Analyst. (PROSE: The Time Traveller's Almanac [+]Steve Tribe, BBC Books (2008). Chapter 3, "Everything Changes"; Page 82.)
On 24 December, 2006, Sally explained to Harriet Jones what UNIT knew about the Sycorax transmission and their spaceship. As she was A positive, she was hypnotised by the Sycorax using blood control and went to the rooftop of the Tower of London. After the Tenth Doctor disabled the device, she returned to normal. (TV: The Christmas Invasion)