I think there's some element of truth when Sayu considers herself the cutest. But I do think she is very self aware of the reactions that statements like that creates and she knows she gets more publicity and air time by amping it up some. It helps make her more recognisable, as a character that generates opinion rather than fade into the background. She has the looks to pull it off afterall. Besides, for every hater, there's just as many who love her (me for one...)