He didn't relax when she knelt in front of him, but he did hold still. He considered answering, wondering if that would keep her distracted long enough to convince her to get back into her coat and go somewhere warm, disarmed a little by her hands on his muzzle, but she was already running past him by then. No thoughts, then, just adrenaline. If she got in the water, she would likely die.
He chased after her as fast as he could run, and leaped toward her, trying to knock her to the ground before she could reach the water. It was desperate, and it wasn't gentle - but anything was better than the alternative of her getting to the lake and freezing to death.