Does this mean you believe she will be discriminated against because of being in private schools?
I don't think it's something that can be considered as discrimination tbh.
AFAIK the issue is that Oxbridge has changed the way they weight GCSE results as part of the application process.
Instead of "just" looking at the results, they now put them in context.
So by way of example where previously they would have "scored" the kids with 10 x grade 9 the highest regardless of which school they attended now they assess the results in the context of average grades of a specific school.
As such if a child is from a school where 10 X grade 9 is of course a fantastic result but not necessarily out of the ordinary for a top flight selective independent school, it won't necessarily rate as highly in the application process as a child's results from a poorly performing state school who got 8 x grade 7's - which was a truly exceptional result for that school.
Also bear in mind that GCSE result are also just one part of the application. They're also looking a predicted grades for A Level and the personal statement.