Alright, so depending on how they play it, I see three possible outcomes.
1)They could just write her like all the other doctors.
2)They could bog down the episode with "hur dur I'm a girl, insert random feminist aesop" (Like they did for the last doctor being old in the transformation episode.) I think (or hope) the writers are self aware enough to realize this doesn't work for any show and even most SJWs won't watch that shit.
3)They could do it like a less edgy Jessica Jones and insert some "feminist" themes while being real about it (or as real as doctor who gets) and make them work by giving substance to the story without shoving feminist monologues in your face.
No matter what though I can already see people complaining that she's a Mary Sue, and I'll laugh at them for just noticing it now cause the Doctor has always been a Mary Sue.