I am almost 1000% sure im building her wrong
heres a link to all of my Diana games on the match history
http://matchhistory.na.leagueoflegends.com/en/#match-history/NA1/209801151?champion=131
dont use the link im not sure how to get it to display right
Match history is broken on your link for me.
This is how pro players build her. I recommend following that if you're confused. http://www.probuilds.net/champions/Diana
i do know that 
is a core item for her, and 
is really good if you are against a team full of tanks. beyond that, i'll leave the advice to the Diana mains :)
I'm assuming your match history link isn't working because the game you're trying to show is a normal game. Idk for sure though
Diana is blessed with being one of the few champions with several fully viable build paths.
My typical build is :
I'll also take 
instead of sometimes.
Nashor's tooth is a fully viable item, I just don't like it as much as I'm typically trying to go in to burst-assassinate targets rather than sit there auto attacking. I've seen people go Wit's End. I've also seen the Morellonomicon instead of a Lichbane. I frankly feel the build I showed you works the best, because it provides you with enough mana to work with, and gives you some big time burst to crush your opponents.
