Irelias E

So recently i was playing against an Irelia, go to lane, lvls 1-2 are fine but once she hits 3 she starts to rek me, now i know how her E works, if i have a higher % of Hp then her it will stun me, Yet lo-and behold, she stuns me when i am at like 50% some Hp and shes at 100...LIKE WTF! i reported her for hacking, but i want to know what you guys think, it sound pretty stupid to me, and alot like hacks.