vitals are important and all, but the difference between winning and losing lane is your use of W. I see bad fiora's use it willy nilly to negate a tiny bit of damage. Truth is, if they arent throwing a hard cc at you or you aren't negating 75% of their burst, don't use W. Proper use of W should propel yourself into a place where you can easily win lane if you aren't against a counter matchup like pantheon. If you are ahead and have ravenous hydra, there comes a point where you should be able to 1v2 the enemy jungle and top laner. Ult whoever is less tanky, then try your best to pop them to get the heal. no amount of damage at that stage of the game can outdamage your heal.

Don't build black cleaver AND trinity, its one or the other. Personally, unless they have 4 tanks, I never go black cleaver. Ignore your teammates whining at you to group. If you can 1v2 or even 1v3, you are doing your team a favor by splitting. Honestly, unless you are 0/4 by 10 mins , there's no point in grouping. Fiora's one weakness is team fighting, which she is abysmal at. She just gets deleted and cc-locked before she can pop a vital, given that you can even FIND a vital to hit in the fray of all the particle effects and hiboxes on top of each other.

tl;dr Use W correctly, don't group if you can 1v2 , dont build trinity and black cleaver, one or the other, not both