A1 at the free throw lane receives the ball from the referee. She than reaches forward with her left leg, over the line, but never sets it down in the paint. Shakes her leg a few times, brings it back behind the line and sets it down. Than she shoots the ball.

Has she violated by shaking her leg across the plane of the free throw line? I know it looks stupid, but is it a violation?

It's technically a violation, as per R9-1-7. She's getting absolutely no advantage by doing her little routine though, imo. If it bothers you, you might tell her to cut it out- your call.

It's ok if she then does it with the right leg followed by the hokie pokie :D