Qin Xuan was overjoyed, thinking Han Sen was trying to teach her. She didn't save any energy and cut at Han Sen with Thunder Knife at full speed.
Han Sen had been practicing Thunder Knife as well recently, so he was quite familiar with the skill. When Qin Xuan just raised her hand, before the skill was launched, she felt she had to stop.
Although Han Sen's hand moved later and slower than Qin Xuan's, he placed his hand at a spot that made her feel very uncomfortable, stopping her from attacking. If Qin Xuan continued her attack by force, her arm would hit Han Sen's hand blade. Qin Xuan took back her hand and prepared to attack again, but the result was the same. Han Sen's hand was again placed at a spot that made her feel very uncomfortable.