Isn't waitress Clara supposed to be from Hell Bent? And seeing as the Doctor's on Gallifrey, perhaps the Gallifreyan Clara splinter who pointed him towards the TARDIS reappears.
"Waitress Clara" is in fact Oswin from Asylum of the Daleks. She's in the episode's final scene and is in fact motivated by the Doctor's story of Clara to go out into space, which we know will end with her becoming a Dalek.