Well it is quite sad actually. She does everything in her power to help him, because she is aware of the many schemes that are ongoing in the other king realms. Seriously, the whole BB revenge was a pretense for getting him a talisman, she was continuously investigating the matters in the Dragon God realm because Shen Xi was connected to Yun Che and there was also the disappearance of all the Yun families there.
Ever since Yun Che met her in the God realm, he has caused her nothing but trouble and worries. She got strong to protect him and herself, but she is still burdened with fighting against the schemes of all of their enemies. She really wants Yun Che to get stronger so that he will be able to protect himself. This is why she is constantly extremely haughty and aloof towards him. She exerts dominance, and makes it clear that Yun Che can’t obtain her both physically and emotionally, because their strengths and backings are worlds apart. Her constant provocation is because she wants to evoke the ambition to get stronger within Yun Che, because she can’t babysit him for all her life.
When Yun Che got permission to take back Jasmine, crimson calamity was about to be solved and he got the backing of the whole God realm, she was clearly extremely happy and smiling from her heart. To the point where she could relax and return to BPS with him after such as long time. It was undoubtly one of the only moments Xia Qingyue completely dropped her haughty and distant act after becoming the Moon God Empress.
But now that Yun Che made an enemy of the whole God realm, she had to yet act and scheme to ensure his safety. The reason she never tells him her true motives is most likely because she knows that he can’t help her with his strength, and if he knew, he would probably try to help her at the expense of his own life. She has told him many times, that she would tell him EVERYTHING if he achieved peak strength in the Primal Chaos and they had no one to fear.