This picture had been given to her by Qi Yuan.
She didn't know whether it had been taken when Mu Feichi made someone follow Han Wanling, or if he'd known from the beginning that Han Wanling was going to conspire against her and so had gone out of his way to dig up dirt on her.
The angle of the photo was very clever. Sun Ming's hand was resting on Liang Xinyi's leg, and her skirt was lifted up fairly high.
Had it not been for what she and Yumo had witnessed that day, she wouldn't have been able to believe that Liang Xinyi would simply sit there shamelessly.
If she really was willing to use whatever means necessary to achieve her goals and was willing to make such huge sacrifices to incriminate Yun Xi, it was fairly impressive.
Mu Fei clearly knew that Han Wanling was trying to dig a huge trap for her and was just waiting for her to jump into it.