She was once a heroine herself but she turned against the Freedom Fighters for Scourge and she helped him take over Anti-Mobius. She loyally cared about Scourge and unlike all other girls he was involved with, he cared about her too,
The B Team Storyline
Slade Strikes Back
Fiona made her first appearance in Slade Strikes Back where Scourge longed to be reunited with her, his wish came true and she helped his New gang as their new team mate. She was however used as bait from Joker who blackmailed Scourge into murdering Oswald but with help from Bender and Lizbeth, Fiona was saved and her hedgehog came out alive. Fiona came with the Team in their endeavors. She and Scourge were the first two alongside Bender and Starfire to know Negaduck was possessed by Joker and she helped Scourge get over it and she realized Star's feelings for Bender rather quickly.
The V Team Island Adventure
She returned in The V Team Island Adventure, pregnant with Scourge's kids and she came along with the Team against Uka Uka and they weren't alone this time. Bender, Starfire, Skipper, Jorgen, Jimmy Neutron, Django and some new friends helped them as well as their bosses Slade and Anti Cosmo. Eventually Scourge proposed to Fiona and made plans with Bender and Eddy to hold it after everything was all settled out. With Bender as best man, Lizbeth as maid of honor and Slade as the pope. The two got married and had children
Unfortunately this happiness lasted only for so long when Marceline's dad made his move and caused discord. Fiona acted like her friends, and when they arrived in the future Fiona was shocked to see her kids being warriors against Darkwarrior at a young age. She got over it and she became protective to her children.
Totally Mobian Spies
Fiona then joined on Totally Mobian Spies with the girls and Eddy to face against Iron Queen and once again Fiona joined forces with Bender, Lizbeth, Skipper, Heloise, King Julian, Finn, Django, Edd, Pinky and The Brain while meeting the Whoop agency, the Sly Cooper Gang, Cadance and Reaver. Fiona definitely has showed us that she is not a girl to trifle with as many have learned the hard way. Fiona next then helps Lara, Sam and Alex save Edd and Clover as they were abducted by Hugo Brass and they have go through a jungle, where she and Lara find a horned creature and work together to beat it