I don't struggle vs Fiora, because I learned how to play Fiora. I know her weaknesses, I know when she wants to go in and when she doesn't. What I see when people complain about her, is "I don't want to learn her, I just want to brainlessly mash keys and win against her!"
Learning the champion you're fighting is key for ANY matchup. Fiora is a champion that punishes you for not knowing. If you don't know to keep her away from your vitals, you take extra damage. If you don't know how to bait her riposte, you're going to find her parrying your CC or big hits. If you don't know how to itemize against her, you're going to find yourself taking the full damage from her autoattacks AND her vital-procs.