Act of Shooting?
 

Rule 4-41-1 says that the act of shooting ends when the ball is clearly in flight, and includes an airborne shooter.

My question has to do with set shots, where the shooter never gets airborne. Let's say B1 fouls A1, just after she releases the ball. A1 is completing her "follow through".

Shooting foul or no?

By rule, no.

In practice, make it a shooting foul unless it's obvious to all that the shot has been released.

Remember, if the player has released the shot, and the defender simply hits the arm on the follow through, it's probably not a foul.