Last year, only 120 pupils in the whole system got 9s in 11 or more subjects. Even with grade inflation, this might go to 200. If they took fewer exams (e.g. 9 x 9) that's still a very small number of people- possibly 1000.
It's less than 1000. But most students don't do 11 GCSEs, so that's not a particularly useful statistic.
All 9s with 7+ GCSEs is something around 0.17% of the population
2019 9 rate was around 4%, per exam.
Clearly getting one 9 is heavily correlated with getting more 9s, but there will be an element of luck. It's not clear that getting all 9s predicts more success than all 9s except for 2 8s, for example.
However it does seem like it would be very very hard for teachers to accurately predict the students who would get ALL 9s. E.g., they might name 10 students as such, but perhaps only 1 student would get it.
So probably she would not have got all 9s, just because it's very unlikely.
However it doesn't matter because some part of this mus tbe a crapshoot, and whether you got an 8 or 9 in GCSE French is irrelevant if you're going to study Medicine or something.