For Her Sake
Wen Sihan was not too bothered about Bai Rouyun and Li Moyun's relationship.
Bai Rouyun was still quite weak and posed no threat to Li Moyun. Even if she said some things she should not say, the one who would suffer the most would be herself, so he was sure that she had a sense of propriety.
Bai Rouyun was relaxing in Li Moyun's arms, leaning against his chest, and feeling quite pleased with herself. Wen Sihan had sworn a Heavenly Oath, so while it was not Bai Rouyun's place to actually decide that he had to swear such an oath, she felt more secure now that he had.
Not for her sake, but for Li Moyun's. If someone found out that he had this book, then he would be chased by the entire world of cultivators, and she could not afford this.