faybelle, in the books, does not believe that villains are allowed to be happy. in some ways, maybe she's right. she says: "villains supposed to be [...] happy. we fester, we dwell, we're prone to years of melancholy. you know, proper villain emotions" (fairy's got talent). she keeps herself incredibly busy to the point of overworking herself for one reason or another--head of the cheerleader team, straight-A student, auditioning for the school play, running herself straight into the ground for the sake of making herself miserable and little else. villains, of course, are not allowed to feel things like happiness or glee.
this is an interesting in contrast to the faybelle we get in the show. we see in forest fest that she is bitter over never being invited to places, the tale of two parties displays her insecurity of others favoring people more than her. there is still that level of negative emotion present; but the part where they differ is in show!faybelle's laziness. she sets up a sweatshop to use people's pets to get out of doing detention, she calls up the fairy mafia to get out of cleaning the school. we never see that drive that characterizes her in fairy's got talent, we are just left with her as a character that delights in other people's pain.
book!faybelle is envious, bitter, and uses evil as a tool for success. show!faybelle is envious, bitter, but her use of evil is something that seems to bring her genuine joy, and her sadistic and unempathic role in the story is interesting in contrast to the more "human" take on her in the books. which one do you prefer?