Question is, why are you trying to harass with your only disable?
Harass with Nova, that way you slow both Drow and Axe.
If you catch Drow farther up than normal you get 2-3 regular attacks in on her as she backs up to safety, and if you see Axe move up towards you, he's slowed so you can back off easily.
Frostbite is all you have to stop someone so you really shouldn't be wasting it on harass unless its a solo lane opponent.
Either that or you worry about using frostbite on Axe if he stays in the creep wave long enough that all of his ally creeps die, and then you freeze him as the full wave of your creeps goes on him. You'll get 3-4 creeps hitting him for damage and your auto attacks.
You're a babysit for AM, really all you're there for is protection and creep pulling when the enemy lane is stronger.