Does Kayle count as ranged for Devourer?

When she's in ranged mode, yes.

She is melee without E active, so she gets 2 stacks per AA

You sould get 3 AAs in before you use E

You got the same answer actually. They both said that Kayle is ranged when she is using E and melee when she is not. They just said it in different ways. :)

From League of Legends wikia Righteous Fury RANGE: 525 / 150 COST: 45 Mana COOLDOWN: 16

Passive: Kayle's basic attacks deal bonus magic damage.

「 Bonus Magic Damage: 10 / 15 / 20 / 25 / 30 (+ 15% AP) 」

Active: Kayle ignites her sword for 10 seconds, gaining bonus attack range, doubling Righteous Fury's on-hit damage, and causing her basic against non-turret enemies to splash to nearby enemies for the duration.

Splash Magic Damage: 20 / 30 / 40 / 50 / 60 (+ 30% AP) (+ 20 / 25 / 30 / 35 / 40% AD)

While Righteous Fury is active, Kayle becomes a ranged champion.

The bold part should clear it up.

If E is active, she is ranged.

If E is inactive, she is melee.