Christina is a thief from a wealthy family who steals for the thrill. After escaping the police the bus she is riding it transported to another planet. Along with the help of the Tenth Doctor the eventually stop the aliens and returned to Earth.
Christina met the Eleventh Doctor again when she obtained the ability to travel beyond Earth after raiding Henry van Statten's sealed vault in Utah. Christina was after a gem called the Eye of Ashaya when the Doctor, Amy Pond and Rory Williams were taking a cruise on a space liner. At the end of the encounter, the Doctor invited Christina to travel with him, but this time she declined, preferring to explore the universe on her own.
At one point in her life, Christina was caught by Adam Mitchell and trapped alongside many of the Doctor's other companions.