Tao'er did not know how Yi Yun had managed to do it. Although she was limited in various ways, she knew that being able to accurately pinpoint her every mistake she made during her control of energy was an extremely difficult task.
Only Desolate Heaven technique grandmasters with rich experience, who often interacted with their disciples, would have been able to achieve this feat of guiding their disciples so well.
If it was any ordinary Desolate Heaven Master, or even any young genius from the Luo clan, they would only be good at the Desolate Heaven technique. But they lacked the experience to guide others. They might not be able to find the flaws during the energy controlling process, let alone guide others in real time during an actual execution of the Desolate Heaven technique.