Her situation is pretty much her own problem now. The only thing you needed to do as a good friend is to point out a few things and then stand aside. They form a new unit, a family. It doesn't have to be the ideal-functioning family (who has seen a family like that?) but it better work out somehow for the sake of the kids. Your friend has to succeed in maintaining the peace and find a type of happiness on her own. It can be bothersome for her to have you constantly pointing out the bad things that are happening. In this way you are cancelling her choice to start a life with this man. You are cancelling her present life and you are only confusing her. Step away for a while. Give her space and if she still considers you as a valued friend, she will process the info you provided her. You were a unit with her in the past, in the previous chapter, as good friends, but things are different now.