Inbounds foul?

[Clark Kent]

Girls Soph game. Game is tied with 28 seconds left. A1 has the ball for a designated spot trow-in along B's end line. B is putting on a full court press. I administer the throw-in and tell A1 that she can move back as far as she needs to as well as told B1 not to cross the black end line. B1 obeys and comes right up to the end line but never crosses the line, jumping and yelling to prevent the throw-in. A1 either didn't hear me tell her she could move back (which I doubt) or didn't care to hear and is 6 inches from the end line. After 3 seconds of not being able to get a pass in and getting frusterated by the lack of space A1 using the ball pushes B1 in the stomach and displacing her and allowing her to inbound the ball to A2.

Is this an foul on A1 (obviously not a team control foul, because it was before the ball was inbounded)? I'd like to hear feedback and opinions on how to deal with this situation.