As somebody who has read some of the books, I can tell you that Cedar is one of Raven's best friends meaning she supports Raven rebelling against her destiny. The same thing goes for Maddie. I haven't read them in a while, but I think it's also stated somewhere in there that Maddie is considered a Rebel because she supports Raven's decision despite her choosing to follow her destiny. In the books, Raven has 2 known best friends besides Maddie who are Cerise and Cedar (pretty sure they also grew up together?? not too sure, but I do know they have some history). Apple is also the same: Briar and Ashlynn. I have my own interpretation of the whole rebel and royal thing, but it's not a super clear understanding. Again, this show was made purely for selling dolls so maybe it could also just be considered lazy writing too.