A husband, in this case, should do his up level best to reassure his wife / first wife of his love for her and spend lots of time in prayer, not only for his own wisdom in how to handle this, but for his wife / first wife as well. I see the following ways of taking care of this and that is :
1) The husband try his best to assure his wife of his love for her and to lovingly instruct her on what Gods word has to say about PM and marriage in general, thus allowing him to rest in the knowledge of said word should he have to resort to the next step.
2) After attempting to do all of the above and said wife is still in rebellion, then he should send her away for a time, ( said time to be determined on a case by case basis ) to allow her to contemplate on what her roll is as wife, what her place is in their marriage and to realize who the husband answers too.
3) If the wife, after all of the above, still wishes to remain in rebellion, then the husband can extend the time apart, he should continue to pray for her and continue to send her Godly instruction from HIS word, in the hope of redeeming his wife.
4) Should at a point in time, the wife becomes involved in or does things that the husband believes meets the criteria of giving his wife a written decree of divorcement, then and only then should he do so, but, only after much prayer.