Can someone explain to me Kayle's AOE attack?

I understand it does AOE damage to you when you are next to it via minion or champion; what about turrets?

How come when she uses it against the turret that the aoe splash is there but doesn't effect you? Just noticed that in today's match. She was able to freely attack my turret with the aoe while I was unaffected by the damage, hence no turret aggro (which would be nice if you were behind and couldn't really do much to her)