Frost was a US Army Major and a member of the Unified Intelligence Taskforce, serving the latter as one of its foremost experts on alien incursions.
She was brought in along with many other experts when a craft of distinctly alien origin crashed into the Big Ben clock tower in London. During the meeting, she sat next to fellow American General Schwartz and, contrary to the rest of her colleagues, was intrigued rather than disturbed by the Ninth Doctor's conclusion that the crash had been faked so as to draw out and assassinate the experts. Unfortunately, he was proven right when the aliens unmasked and identified themselves as the Slitheen family before electrocuting the experts via their ID cards, killing all except the Doctor. (TV: Aliens of London / World War Three)