* Fiona Fox is a character from the Archie Comics Sonic the Hedgehog series, not the main games.
* She wasn't originally a villain. She started as a friend of Sonic and Knuckles, but was later revealed to be a double agent for Dr. Eggman.
Therefore, Fiona Fox is not considered "bad" in the Sonic games. She is a character from a separate continuity that has a complex and evolving history.