"Princess Zhu Huan" Wei Zi is obsessed with finding her father. What is this for?

It is clearly explained in Princess Pearl.

Wei Zi didn't tell the Swallow her story, but the Swallow couldn't listen any longer. The swallow said angrily, don't look for this kind of father, he is unforgivable at all, just pretend he doesn't exist. Wei Zi knew that his father was incompetent at all, but he still tried his best to find him. Wei Zi also showed his determination to the Swallow. Then Wei Zi explained to the swallow why she had to find the father no matter how hard she tried.

Wei Zi said to the Swallow, It's not that I won't give up looking for my father, because my mother loved him all her life. Before she left, she urged me to find my father. The reason why I am so persistent is that it is Xia's last wish, and Xia insists on doing so. Moreover, when Xia Rang went to look for it, he must ask: Do you still remember the summer by Daming Lake?

But why don't you come and find it yourself after all these years of summer? Because Xia always believed that Qianlong would go back to find her, Xia waited at home until she died of old age. Xia's life is like that sentence: I waited all my life, complained all my life, thought all my life, and loved all my life.