While on her way to Ypres in 1917, she was abducted by the War Lords and hypnotised into participating in their simulated version of the war. She and Lieutenant Jeremy Carstairs overcame their conditioning thanks to the Second Doctor and they helped him organised the resistance against the War Lords. Like all the surviving victims of the War Lords, she was returned to her proper time and place by the Time Lords. (TV: The War Games)
The Second Doctor met Lady Jennifer and Lieutenant Carstairs again in 1915, wanting to confirm that they had been returned to Earth safely, quickly ascertaining that they had no memory of having met him. The three of them helped Winston Churchill escape from the Players who had captured them, with the Doctor staying behind to keep the Players at gunpoint while the other three escaped in a plane that would have taken Churchill to Germany, the Doctor advising Carstairs and Jennifer to recognise that they were made for each other.
Over the next two decades, Jennifer and Carstairs were eventually married, with Jennifer dropping her title (although she jokingly commented that she was waiting to use it again when Jeremy got his knighthood). She later met the Sixth Doctor when he collaborated with Churchill and Carstairs to thwart a Nazi coup of Britain, although he posed as a different man to avoid awkward questions. (PROSE: Players)