Yeah, she does mostly physical damage so armor is better than health, and percent health true damage doesn't factor in shields so you want Bloodthirster, a Sterak's, or a champ with shields.
The big thing about her though is she's on the low end of ADC range and she's very squishy so what you really need is a reliable way to CC her even if she ults. Get a TF (so he can ult when she ults), or a Cho'Gath, or a Janna, or even a Taric. And a Zyra helps too, since she has a hard time dodging her E, especially if her tumble is down.
Also play a carry with a decent amount of burst, basically anything but Blue Ez (all other Ezreals can do fine as long as you've got some way of CCing her).