Original: On Christmas Eve, the day of her wedding, she is accidentally pulled into the TARDIS as a result of being dosed with Huon particles by her duplicitous fiancé, Lance Bennett, on the orders of the Empress of the Racnoss.
Simplified: On Christmas Eve, the day of her wedding, she is accidentally pulled into the TARDIS because eshe has been drugged with Huon particles by her fiancé, Lance Bennett, because he was tolf to do so by Empress of the Racnoss.