The determination of the crime of intentional injury must first have the intention to cause intentional injury, and secondly, it must cause certain consequences. The nanny's behavior is indeed hateful and may seem worrying, but in fact it does not constitute a crime unless it causes some harm to the child and cannot be prosecuted for intentional injury. If injury is caused, there is absolutely no problem in prosecuting the crime of intentional injury, and the penalty will be heavier.
Abuse is a personal accusation and cannot be ignored. Generally speaking, beating a child by a parent does not constitute a crime of cruelty, let alone a crime of cruelty. Who beats his own child cruelly?
But in any case, hitting a child violates the Law on the Protection of Minors and does not constitute a crime. You can also tell the public security organs and you will be punished accordingly.