Tristana W

I was ashe vs tristana and every single time i could R her she would just jump away as if my arrow had never hit her, i'm very confused as to how this mechanic works when my cc goes off before the animation of her W is even being buffered. And its not like the cc is still going through when she completes said jump, even when it was a longer range arrow the stun duration seemed to be nullified by the jump. I understand the whole idea of input buffering and her jump taking precedent, but when the animation isn't being channeled beforehand, and is instead being channeled when the crowd control is already on her doesn't make much sense.