Well, the parents need to act swiftly. They should fire the babysitter without hesitation. After that, they could seek professional help for the child if they think the child has been affected psychologically. This could be in the form of talking to a child psychologist or a counselor. At the same time, the parents may want to spread the word in their community to prevent other families from hiring this babysitter. This is to protect other children from potential harm.
The parents should immediately terminate the babysitter's services. It is a red flag behavior that cannot be tolerated.