Can a mother force the childs father to sign his rights over in Nevada? 50/50 custody, court ordered.....?

I have this friend, his daughter is 11, she lives with the mother. The mother and father were married, but have been divorced for years. She told her dad she doesnt want to see him anymore and wants him to sign his rights over. The mother just calls him names and says he has to sign his rights over or she will take him to court and she said he will end up in jail! When they went to court for custody, the judge awarded 50/50, and the child lives with the mother. The mother dont work, and her and the child live off the child support that the childs father pays, along with state aide. The father sees her and also pays child support and is up to date. The mother has 2 older children(not by my friend) that have told him to sign the rights over also, kinda threatening my friend. What can my friend do? She cant force him to sign his rights over? Who should he call to talk to or ask about what his X wife is doing? Can she get in trouble? Any answers are appreciated and opinions too! Wonder if anyones been thru this?