She is really all about attack speed.
Her base AD is one of the lowest in the game, and her AD ratios are pretty disappointing.
Her passive is really what makes her viable since it ultimately scales on the target's current HP.
Bloodrazer is good because it also scales on maximum HP so it becomes effective as the enemy champion reaches lower health, while working with her passive by increasing attack speed.
Runaan's is mostly good because of it's passive that applies on-hit effects, including her passive.
Blade of the Ruined King would be good, but probably wasn't on the recommended build because it had recently been buffed.
As I mentioned, her base AD is super low, but still having some AD is definitely helpful since her passive does have a diminishing return, this will help to normalize that, but overall attack speed is still your main focus.
Now, DESPITE her low base AD, she does have some pretty low cooldowns, which means Spellblade passives tend to work quite well on her. You might consider trying Trinity Force or Iceborn Gauntlets on her as they will help provide her with extra damage and utility to stick to her target. For a slight bonus in combination beyond that with added safety, I like to pick up Sterak's Gage.
As for other items, ... despite my understanding of her kit, I'm not an expert when it comes to actually playing her, so I don't really know what others would consider meta at the moment.
My suggestions may honestly be absolute garbage lol.