I think what Robbie is saying is that maybe the SS was thinking she could tag R1 going from 2nd to 3rd OR throw to 1st and that's where the dancing came in. The SS may think it was 1 out and she was holding R1. HTBT, so I don't necessarily agree with the interference call.
BUT----I have to agree with Mike, the coach should not have touched the batter/runner. This is not 10U Rec ball, dead ball, batter/runner out for assistance game over, head for the parking lot.
