I know it already has a delay, but if the Annie does flash R in quick succession, it's almost impossible to react to that in time.
I know you're trying to make skill rewarding for Annie, but it's already too damn rewarding (52.45% win ratio), and you're forgetting about the reward for reacting to it.
The cast time should be increased, but it should still be low. Just high enough to allow good players to flash away from it if they're focused on it.
Don't "Veigar" her.
I'm also curious on knowing what the current delay is.