The answer is He started to talk, but she cut him off with a commanding wave of her hand.
He stopped talking when she started waving her arms all around. is incorrect, because that is not what she did
She started yelling and waving her arms at him, but he kept on talking. is incorrect because she was not yelling
She was talking, but then he gestured commandingly to her, and she stopped. is incorrect because the boy, not her, was talking
