" Waitaminute, she's not a villain at all! " You're right! She isn't & never was!
Sara is a half-human/cat girl who grew up on the peaceful South Island with a loving dad. Years passed & she & her dad ( who is now the President of the island ) witnessed the appearance of Sonic during a battle with the notorious Dr. Robotnik. A now teenage Sara grew fond of the hedgehog after meeting him upon various attempts by Robotnik to kidnap her.
The most recent attempt being Robotnik's most successful yet, taking Sara hostage as his latest creation, the Hyper Metal Sonic, nearly destroyed the island & Sonic along with it! However, with the help of Sonic's friends Knuckles & Tails, Sara was saved & Metal Sonic was destroyed after a fault in it's programming caused it to sacrifice itself to save the president from a fire.
Being the President's daughter, Sara's got just about everything a teen could want ( materialistically anyway ) leaving her with quite the spoiled & bratty attitude. Because of this, not getting her way or seeing her friends in danger throws her into quite a fit. She packs a good punch & could probably kick someone's butt with enough combat expertise!
Despite her sassy & snobby demeanor, she really cares for those around her & doesn't have an evil bone in her body... Then perhaps there's another reason why she's working with such a menacing pack...?