You know who is the Yellow Dress Maiden Yang who suddenly came to Shaolin, and solving the Zhou ZiRou problem for Zhang Wuji.
If we talk from the perspective of a writer, this Yellow Dress Maiden is basically the ultimate Deus Ex Machina moment created by Jin Yong to rescue the situation. You can see it, an unknown character who previously no where to find suddenly come to the scene to rescue the situation. So whatever you think about it, you can't deny that it is basically a blatant deus ex machina moment that should be avoided by any writer nowadays in modern time.
Because if she's really that busy body, why she never came to rescue the situation before the last moment in the novel? You can see it. There are a lot of dangerous situation in the story. From the death of Zhang Wuji's parents, the invasion of Ming peak, the kidnapping of China's martial artists, etc. that the event actually has more weight than the fight for Xie Sun in Shaolin Temple. But she never appeared.
So why she suddenly came to Shaolin and beat Zhou ZiRou when the situation become ugly for Zhang Wuji side?
Let us take aside the real world situation of Deus Ex Machina moment. I think She became aware of Zhou Zirou when Zhou came to Peach Blossom Isle, after she got the map from both sword and saber. So, I don't know about her motive, but I think she has the responsibility for the books that Zhou were taken. Because those books were mean to the leader to beat Mongolian invaders. So when she saw that Zhou ZiRou when astray in Shaolin, she didn't has any reason to not intervene. As it is the Peach Blossom Island responsibility for giving Zhou the books.
What do you think about that?