When did Luo Yu in The Biography of Yan Xi Maid-in-waiting discover the murderer of his sister?

Wei Yingluo found her sister's killer in episode 25.

Wei Yingluo went to Ye, only to find Ye tied up. Just when Wei Yingluo felt something was wrong, the eunuch at the back had picked up the rope for her. Wei Yingluo struggled for a moment, and as he lay dying, he remembered that Ning was murdered in the same way. His will to survive broke out and he broke free from the rope. Fortunately, Fu Heng appeared at this time to help solve the eunuch. Fu Heng believed that this was the result of Wei Yingluo's determination to retaliate and advised her to be cautious. Wei Yuluo thought that the emperor wanted to kill himself, but Fu Heng said that it was natural for the emperor to kill her, so there was no need to be so secretive. When Wei saw this scene, she knew that Princess Jade wanted to commit suicide.

Seeing that pleading with the queen mother was useless to Wei, Princess Jade simply found the emperor and sent someone to bring him his favorite snacks. When the emperor saw the dim sum, he remembered that Hiroko had robbed the dim sum and saved his life. He knew that Princess Jade was reminding himself that he owed Hiroshi his life. Wei Yuluo deliberately sent Yu a box, which was actually the hand of the eunuch who murdered himself. Yu and the maid-in-waiting were frightened when they saw it.