I'm not sure which novel you're referring to because you didn't provide enough information. However, if a female protagonist's servant girl was called Jingxin, it was usually because one of the characters in the novel was a servant girl of a female protagonist, and the name described the servant girl's personality, appearance, and other characteristics. Of course, it could also be because the name or plot of this novel was related to the name " Mirror Heart." If you can provide more information, I can answer your question more accurately.