After the Cultivation Secret Skill was made public, Du You began to use it openly. Of course, he used it on Xiaobai.
Xiaobai's cultivation method was different from others, as it had been improved by Du You. It wasn't something widespread. If it were someone else, they wouldn't cultivate in such a unique way.
But Xiaobai was different; in her heart, Du You meant everything, and she would listen to whatever he said.
As a result, Xiaobai used the new method, and her cultivation speed increased. In less than a year, not only did Xiaobai stabilize her strength at the first tier, she was close to reaching the second tier as well. Before entering the Outer World, Xiaobai should be able to reach the second tier. With second-tier strength, unless one is particularly unlucky, there shouldn't be any problems.
