Basically, Felicity would be feeling too overprotective of Shinsou and paranoid after Unto the Cruel. She'd be desperate to get stronger to prevent anything like that from happening to her loved ones again. She'd somehow gain the trust of the Fallieni in Part 3 (can't be in parts 1 and 2 cause she's in Phantaria with Gwenael during that time period) and learn traditional Fallien martial arts plus Joshua's new one.

And Felicity will finally meet Joshua so yaaayyyyyy!