OP,
Now that we know your DD’s super PG’s I’ve had another look at other, stronger options she might want to consider. In no particular order:
The London uni with the strongest rep in the Humanities is UCL. Even your DD’s earlier PG’s met their stated admissions requirements, somewhat to my surprise. Now she is looking like a star. Their only Joint Hons programme involving French is French and Art History so I don’t know what she would think of that.
Also U London has a degree programme in French that is offered in Paris, for the ultimate Study Abroad experience.
I had briefly mentioned Edinburgh. Turns out they have a programme in French and Francophone Studies. The latter incorporates history, philosophy, culture, etc. It looks very interesting. The standard offer appears to be either AAA or AAB.
Finally, given PG’s of A star AA, what does she think about applying to Oxford? (A better city than Cambridge IMO.) The stated admission requirement for French - they offer degrees in both Language and Literature - is AAA. (In practice it could be higher.).
Now, most qualified applicants will be rejected so everyone applying must do so robustly. I remember you started this thread by characterising your DD as a bit of a swot, but you also said she has a passion for learning and this is what Oxford want. The tutorial system could be just the thing for her. She already knows how to work hard. Time and time again I have seen students rise to a challenge.
If she is at a school that sends a number of pupils to Oxbridge and trusted teachers really think it would be too much for her, I as her parent would give that serious consideration. But schools that don’t know much about the Oxbridge system tend to overestimate the giftedness of their students. Of course more than an average share are brilliant, but plenty of others have been sweating and prepping with the best teachers and private tutors for years. It sounds like your DD has been self motivated. Don’t let anyone sell her short.