Based on Gu Nianzhi's understanding of the Tan family, there was only one person who, as a last resort, would be able to stop the two crazy parent-in-laws, Cai Songyin and Tan Dongbang. It was their precious daughter, Tan Guiren. However, how Gu Nianzhi felt about Tan Guiren was complicated.
Up until now, Tan Guiren had not exactly partaken in anything that could exactly be regarded as a misdeed. She wasn't someone like Gu Yanran and was definitely not someone like Wen Shouyi. Those two people had brought upon her harm that was substantial and irrevocable. It would be impossible for Gu Nianzhi to reconcile with them.
Tan Guiren, on the other hand, was a little better than Xu Piaohong and Gui Suyao.