She’s got a very light acting resume, but she fulfills the basic requirements for a companion: Female, human, incomprehensible English accent, and wears casual clothes, including tennis shoes so she can RUN!
Andrew Liptak on iO9 has the lowdown on Doctor Who’s new Companion. (which actually isn’t much).
— Doctor Who Official (@bbcdoctorwho) April 23, 2016
Doctor Who seems to have gone in a completely different direction than with Clara, while still keeping within the parameters of young, female, spunky, middle- or lower-class and British.