Originally a member of Torchwood, Krista became a member of UNIT after President Harriet Jones merged the two entities, along with The Preachers, into a single organisation. She told Jackie Tyler that Pete's World's Earth had not experienced alien incursions to the same degree as N-Space due to the power Cybus Industries wielded.

Krista had been severely affected by the death of her daughter, who was one of the many Londoners controlled by their EarPods and converted into Cybermen at the Battersea Cyber-factory. She stated this was the event that inspired her to join Torchwood. However, after discovering the Meta-Crisis Doctor was growing a TARDIS, she held him at gunpoint at UNIT's Big Ben base in an attempt to force him to take her back to save her daughter. After Jackie diffused the situation, the Doctor reported Krista as a threat to UNIT, despite promising otherwise, explaining that she needed to be arrested and that he gave "no second chances". (AUDIO: The Siege of Big Ben ^[+]Joseph Lidster, Short Trips (Big Finish Productions, 2018).)

Jackie remained upset with the Doctor for how he betrayed Krista. (AUDIO: Flight Into Hull! ^[+]Joseph Lidster, Short Trips (Big Finish Productions, 2018).)