No, windwall does not work on her AA. Neither on the attack itself, nor on the AOE. It´s not a projectile. And if it´s not a projectile, it passes through windwall like it wasn´t even there.
Some things that work on Kayle's favor? Unless the Kayle player is braindead, the matchup completely favors her because of how she works. She doesn´t need to be close to Yasuo to wreck him.
The greatest weakness for champions with high mobility like him is slows/snares/stuns.
He takes a waveclear/crit/AS item first while she takes an AP/AS/CDR/Oh-hit Magic damage item.(Statikk vs. Nashor's) Her item has a lot more stats and a lot more synergy with her kit.
Kayle isn´t as squishy as everyone presumes her to be. Her status as a Fighter is pretty justified. Take a Rylai's and boom, you just killed one of Yasuo's main ways of chasing down someone. She gets HP and a modest amount of AP from it. With an extra slow on hit.
Her ult > His ult. Simple, really. He ults. She ults right after his ends. She heals herself with W, slows him with Q, brings up her E and chunks him down before her ult ends.
Yasuo is more of the damage kind of champion. Kayle, much like Ryze, works more with resistance reduction than pure damage.
Reduces MS and AS. Yasuo needs those. Reduces his Armor and MR by 10 flat points. Synergizes perfectly with her passive. Reduces damage dealt by 40%. Those crits suddenly aren´t all that powerful. All in 2.5 seconds, which is all she needs to destroy him.
She directly counters him. It´s not being edgy. OP stated all the right reasons as to why it is the way the is, much like i´m doing right now.