Christina is a villainess from the 19th Fansadox story Starfuckers: Episode 1 by Roberts. She seems to be based on Christina Aguilera, and her victim on Britney Spears.
A rich client has organised the kidnapping of singer called Britney. She is to be taken to a private island where she is tortured and sexually violated as part of a sadistic show for the client.
Christina has been hired by the client to participate in Britney's ordeal. She is first seen pleasuring herself to a live feed of Britney being tortured, she then goes down to the dungeon area to participate herself. She sexually violates Britney in all sorts of ways and tortures her with a whip.
However she seems to take far too much sadistic pleasure in what she's doing, and goes too far with the torture as the client didn't want Britney completely destroyed. Christina is then taken away under the orders of the man supervising the session to be punished for getting out of control.