Katarina Itemization Questions

Katarina more often than not builds full AP maybe with a Gunblade depending on the katarina player. The thing is though is that she has Scalings on her Passives knife pickup, her E and her R that while it's only bonus AD her ultimate for example scales with 285% AP and 330% bonus AD. So what i'm asking is if it's worth picking up one of the new AD assassin item on her such as Edge of Night, most of her new kits damage comes from her passive, q and r and two of those have amazingly high AD ratio's so why not?

(note she still only does magic damage with them so of course the lethality stat is useless on her but still i'm curious)