1. From Hua Fei's mouth, we can know that Cao Guiren was originally just a poor housekeeper. Thanks to Hua Fei's blessing, she can give birth to a child, and she can also raise Princess Wen Yi herself. This means one thing. Cao Guiren is poor and humble, so according to An Lingrong's example, there is a high probability that she has no loyal minister like Liu Zhu Huanbi since she was a child. Then her maid may have been in the palace from the beginning.
2. Because Cao Guiren was poor and gave birth to a princess, he was bent on saving her dowry and making a living under Hua Fei. It is impossible to live a hard life. Even Zhen Xuan said that she didn't have any decent jewelry at ordinary times, so you can imagine how poor she was. What money can such a poor man have for his servants? Cao Guiren's original maid-in-waiting was in the palace, and she didn't like Cao Guiren. Cao Guiren didn't have enough money to buy her heart, so it's not surprising that she chose to betray Cao Guiren.
3. Another important reason is that at this time, Hua Fei has fallen, and Cao Guiren's greatest dependence is gone. The emperor never came to see Cao Guiren, because Cao Guiren was a princess and a princess. At this time, Hua Fei fell down, and the queen mother also said that the princess could be raised by others. Therefore, when the emperor chooses to deal with Cao Guiren, he must also give a message to Cao Guiren's servant girl, that is, Hua Fei has left and the princess is leaving soon. So what does Cao Guiren have to miss? What's more, if she doesn't do this, the emperor is not short of hands. In case this servant girl does well.