Obviously, the other nobles don't show their contempt or jealousy infront of the royal family. That would cause them to lose face and be less highly regarded. They only show and do these things behind the backs of those who are actually friendly with the Chiffons, and sometimes even then slipping up. Solia wouldn't likely know anything about this because:

1) When Mystere visisted, the two of them aways played alone - no other children were involved or present.
2) Mystere would never actually bother to tell Solia about these matters.
3) Considering the Chiffon-family doesn't visit the Capital province, where the royal family lives, particularly often, these rumors are mostly spread through the other provinces and castles. Even the King and Qyueen, who were somewhat aware of this fact, didn't have a full grasp on just how widespread and severe this dislike for their friends were.

See-through skirt, cleavage, open back, butt-cleavage... And fox-ears. She's got it all~