Irelia stun doesn't work if Foira ults.

I was playing as Irelia top lane against Foira. I noticed several times if I used my "e" with lower health than her (I was at half she was at full, health) and she used her ult either at the same time or a fraction of a second after my spell. My stun would not go off and her ult would go through, but my stun would still be on cooldown. If a spell is on cooldown, it means it went through, only it didn't.