Personally I feel like she's one of the most annoying champs to go against in top lane because she scales really well but she doesn't appear to have any clear weaknesses early/mid. Ok I'm not a top lane main but that's what it seems like.
What I've noticed is that on the forums there aren't people who try to defend her. But there are plenty of people who hate her. Whenever the idea of nerfing something else that's strong in top lane comes up somebody will inevitably point out that it would remove one of Fiora's checks, making it harder to deal with her.
It seems like she's a relatively strong top laner due to lack of clear weaknesses, some other strong things keep her in check, and nobody actually likes her.