Who is to judge what the definition of "world class" means? Both of these schools, CLC and Roedean, are great! You need to choose which one your DD would feel happiest in as they are so different.
I would challenge that Roedean is only the girls Eton. At Eton exam results and achievement (both in the classroom and extra curricularly) are very important. It's a competitive place, as the OP would know having a DS there.
Roedean A levels: 22% A, 56% A-A vs Eton 33% A and 75% A-A (and they also do Pre U so these results do not tell the whole picture)
GCSE Roedean 9-8 52% vs 79% Eton and A*-A 68% Roedean vs 93% Eton.
Also Eton is fully boarding, whereas at Roedean 82% of KS3 are day girls.
CLC is more like Eton in that it is 80% boarding (fully boarding, not flexi or weekly, with a full programme of weekend activities for all boarders). Also its results are more like Etons
A level 32% A, 72% A-A plus an IB score of 40 points for those who do IB. GCSE 9-8 74% and A*-A 90%.
Roedean says 55% of girls go to Russell Group unis which doesn't seem very high to me.
Posters are right that you must go with your gut instinct about the feel of a school and find one where your DD will thrive.
FWIW, I think Wycombe Abbey is probably the closest girls school to Eton in terms of exam results, competitiveness and full boarding characteristic.