I don't really mind her myself, but what if...
Fiora had vitals on herself, as well as her opponent?
Obviously, the damage Fiora takes from this would probably not scale with her opponent's stats, but I feel like this would solidly reinforce her duelist identity.
This could only occur after Fiora casts an ability if it constantly being up is viewed as too big of a penalty, as that would accentuate the action-reaction nature of Fiora better anyway.