It's better to ignore it. Typical brainwashing, fear and hopelessness. This subservient role will always be a matter of fact in the Society. There is no toleration for disobedience. The child is considered the step-father's grandchild.
Nothing is questioned.
The mother actually after a time, protects and defends the relationship her husband has with her daughter. Some slip into denial and merely behave as obedient slaves to the husband. Yes, but she will face ridicule, possible disfellowship and harassment from within the congregation. Besides, the judicial board is made up of males from the congregation. There would have to be at least two witnesses and that's no guarantee that there will be anything done.