No matter what opinion Shen Biran holds about Gu Qingyuan, that opinion will never manifest in her interactions with Gu Xiaonuan.
There's no other way; it's best if Gu Xiaonuan knows nothing at all. Otherwise, there will inevitably be more trouble in the future, and these troubles will make Gu Xiaonuan realize what Shen Biran has done without her knowledge.
Gu Qingyuan doesn't care about what's happening in front of him. If he did, he naturally wouldn't have so many issues arising.
However, all these problems merely highlight one thing: under such circumstances, no one can say anything anymore. No one can go to Gu Qingyuan to explain, nor can they harbor any unnecessary thoughts.
Gu Qingyuan won't consider Shen Biran's feelings, so there's no need to worry about how he will be treated.
Things happen for a reason, so there's no need to ponder over why such situations occur.
