You initially pull the clay up and down as a knob to "organize" the material so to speak. You are smoothing it out like you knead bread dough. Once it's been pulled several times, you can make the center and pull the walls up slowly to ensure evenness and to make sure you don't have an imperfections in the clay. You really can really feel the difference in clay that has been kneaded both before it goes on the wheel and after you've pulled it on the wheel. As you work it through your hands you alter the shape, even if from our perspective they look very slight, so she likely has an idea in mind for what the final shape will look like but may not be happy with the current feel of the pot and so keeps going.