Paternity case

My lady friend is separated from her husband for 3 yrs now since 2008. She had an affair with a married man who got her pregnant. When she gave birth, the child carried his legal husband's name with the permission of her legal husband. Her affair with the married man was very violent since the start. She would have wanted to get out of the affair but the married man would always threaten to ruin her (My friend occupies a high position in a government agency) and file an administrative against her for immorality. He would sometimes get physically violent everytime she tries to end the affair. There are also threats of the married man to file a paternity case to prove that he is the biological father of her youngest child. Though this may be true, the child is considered legal child of the legal couples and has been accepted by the legal husband. Can he file a paternity case against my friend to prove that he is the biological father? What are legal remedies that my friend can employ to finally break free the affair and protect her and her kid from the harassing married man. Pls help.