Fiora's ulti works through stun

Anyone else who have seen this? (Fiora's ulti works even though she's stunned.

Yesterday me and some riends played ranked 5s and i played Annie, so i lure Fiora towards me so that our team could kill her quick. when she came close enough i stunned her. Clearly visible stun with "icon" above the head and she stops for like a 10th of a second and then she pops ulti on all of us.... WTF?! Riot.....

Is she suppose to break a stun with her ulti, then she needs a serious nerf...