In the TV series, after Yoyo's mother leaves, Yoyo may find it difficult to accept and face this reality, so she chooses to suppress her emotions and avoid thinking about her mother and asking why she hasn't come back yet.

This may be to protect yourself from greater harm. When faced with the death or departure of a loved one, people may choose to deny, avoid, or suppress their emotions in order to be better able to cope with the situation.

In addition, Youyou may also think that her mother left because of her, so she feels guilty and self-blame. This emotion may make her even more reluctant to think about her mother and ask why she hasn't come back yet.

In short, the plot in the TV series may be to better express Yoyo's emotional changes and growth process.