Is Akali W supposed to work this way?

So I just got out of a ranked game and something was bothering me about Akali's W that game. Before anyone asks, yes we lost cause Akali got fed. No I'm not mad or salty, more confused about a certain interaction that kept happening.

She'd use it, go 'super-invisible' to dodge targeted attacks and then a couple times either my Swain would hit her with his E or I (a Janna) would knock her up with my Q. We would see the damage flash like what normally happens when you hit invisible champs with abilities, though because she was in her W Swain couldn't click her to passive pull her. That's fine and makes sense.

What I'm confused about is there were 3 separate times she would dive in on me or my Kai'sa and instantly drop her W to dodge the reactions. All 3 times, I ulted to push her away.

IT NEVER WORKED. [sg-lux-2]

Akali can't be 'targeted' when in her shroud but as mentioned, she could be hit by generic AoE abilities. So why couldn't a Janna ultimate, a large AoE, push her away when my Q could still knock her up? I chose Janna specifically to keep Akali and the enemy Diana off my adc so I want to know why one AoE works but another didn't. Is it a glitch? Or is she immune to being pushed out of her W by AoE while still able to be hit in it by them?

[sg-janna]