Amber is serious about her work as Chad's fan club president, as evidenced by her having a fanclub business card. She had also dressed up in disguises and costumes (Smooth, Maya Baboodi) to fool Tawni, Nico, and Grady into telling her what they had thought of Chad after he started dating Sonny.
Amber had concluded that Sonny was the reason Chad hasn't been getting any more fans on Flitter (a parody of Twitter) because ever since Sonny started dating Chad, Chad had become a nicer person and that his fans preferred him the way he used to be, meaner and inconsiderate.
She was furious when Chad decided that he'd rather have less fans if it meant dumping Sonny, causing her to flitter lies about Chad to make his fanbase go down even further. Amber seems to dislike Sonny for making Chad's fanbase go down, and for being part of the reason Chad fired her from her job. She tried kidnapping Chad to keep him from seeing Sonny, but Sonny had freed him and her castmates by wearing a convincing disguise of her own (Carlos La Cienega).
Amber is currently the ex-president of Chad's fan club, as Sonny has taken her place but Sonny failed and Chad just went on with how many fans he has.
Amber is originally from Houston, Texas.
She was possibly also jealous of Sonny being Chad's girlfriend.
She was required by Sonny to get back all of Chad's fans, and to stop flittering bad stuff about Chad.
This was Raven-Symone's big Disney comeback since That's So Raven.