Why can't Ni Kun speak Chinese?

Although Ni Kun's mother came from China, she immigrated to Thailand when she was very young, so in fact, her mother doesn't speak Chinese well now. . . Not to mention the relationship between Ni Kun's family environment and studying abroad, of course, she can't speak Chinese ~ but Ni Kun is very smart and should be able to speak very well after learning, but now she only knows a little commonly used ~