Bernice Summerfield and Keri were old friends who worked together on numerous occasions. (AUDIO: Making Myths) They first met on the planet Peladon in the 40th century. (PROSE: Legacy) Keri attended Bernice and Jason Kane's wedding in Cheldon Bonniface on 24 April 2010. (PROSE: Happy Endings)
After she had finished her travels, Bernice worked with Keri again several times in the 26th century. One such occasion she interviewed Benny about the lost fields of Aggravar. This involved going to the expedition site, where they fell into a cavern where they found more evidence of the myth. (AUDIO: Making Myths) However, their relationship was seriously affected when Keri lied to Bernice, putting her in serious danger whilst in the pursuit of good ratings. (AUDIO: The Goddess Quandary)
Braxiatel later moved Ker'a'nol's personal timeline backwards thousands of years, rewriting her life to match Bernice's period on the Collection, doing this without anyone having noticed. (AUDIO: The End of the World)
At one point, the Doctor took Keri ice skating on what he told Keri was a frozen planet, that turned out to be a giant alien creature the Doctor named Torvalundeen. When the creature laughed at the pun, causing seismic tremors, Keri fell and broke her leg.
Later, while her leg was still in a cast, the Twelfth Doctor met Keri at the White Rabbit on Legion, where they had both been summoned by mysterious postcards. The Doctor gave Keri a smartphone with universal roaming so she could remain on Legion and do some research for him. Later on, she elected to remain on Legion with Bernice Summerfield and her friends. (PROSE: Big Bang Generation)
Sometime prior to this, Keri had met the Doctor's friends Sarah Jane and Luke Smith. During that incident, Keri became "possessed by the ancient spirit of the Kortha Gestalt," which prompted K9 to shoot her. The Doctor was not present for this himself, but Sarah Jane and Luke related the story to him, saying that Keri was not best pleased at having been shot. (PROSE: Big Bang Generation)
Behind the scenes
The Twelfth Doctor novel Big Bang Generation by Gary Russell features Keri, and briefly describes several heretofore-unseen previous encounters between her and the Doctor, though no indication of which Doctor is given. Keri does not seem surprised by the Twelfth Doctor's appearance, however, so it can be presumed that she had at least met him in that incarnation before the events of the novel.