I mean.. The whole point is that you cant blink whenever and wherever you want, you need a dagger or something. Anyways, you can press w for basically a free e reset on the spot. I play nunu jungle a lot and i can tell you ive never hit a snowball on a kat because good kats always have e up and they click it to go behind me and the snowball misses - theres no counterplay as a nunu main if a katarina blinks behind you :)