[Cueballmania]

I believe the answer is that we tend to reduce force to an equilibrium. Think about pushing a large box across carpet. A constant force should keep the box accelerating. I know when I push a box, the force decreases after I get it started and it reaches a steady speed. My force has reduced to equal the force of friction just as your force has reduced to equal the force of her arm.

Friction is not the driving force, this is a two forces problem. I'd hope that the torque in your arm can overcome air resistance.