That's Dark Wing's Woman

When Hua Feihua explained the truth to Li Yi, Li Yi had already determined that Princess Huaiyu would not release the clip.

After all, there were three people involved in the clip.

Hua Feihua, Milk Dipper Solitary, and Yang Xingchen!

Hua Feihua had told Li Yi that she had no idea that the clip had even existed, in other words, it meant that she was not the one who recorded it.

As for Milk Dipper Solitary…

While Hua Feihua and Yang Xingchen were doing it in the bedroom, Milk Dipper Solitary was in the living room. As such, their act was done without the knowledge of Milk Dipper Solitary…

Thus, as it was neither Hua Feihua nor Milk Dipper Solitary who recorded it, the only choice remaining was Yang Xingchen, and no one else.