What if the dad is the slep father he files for a divorce then he refuses to let the mom or her family take her and child protection wont help or ivestigate they say step dad can keep child with moms?

This sounds like a Family Law Court issue rather then a child protection issue. Generally, statutory child protection agencies will not become involved unless there are significant concerns raised relating to the well being of the child. The child needs to have suffered physical, emotional or psychological harm or be at unacceptable risk of harm prior to Child Protection Agencies becoming involved. Please note that each country and state has differing legislation and thresholds so this may not be the case with your local child protection agency.