Fiona is trainable on easy mode at least. The enemies are lower level, so you can change your DB members from chapter to chapter in part 1. She needs just a few levels and points in strength (maybe energy drop) to use a steel lance without speed peanlty. Give her a support with Nolan, Volug or Zihark and she will be a dodge tank. And Fiona has two very nice free skills and canto!