Thanks for the reply.

Actually, that wife has mental problem and my friend and that guy are planning to get married once the divorce is completed. However, that wife does not want to leave and start to go crazy: pulling a gun out, chocking the guy, throwing things around, calling and e-mailing to threaten my friend... I agree that she should probably better off dating a single guy to start with but it's too late for her. Everyone has his/her own perspective and I respect that. I don't want to be judgemental. As her best friend, I just want to help her to go throught this hard time. I would like to see if there's anything I can help her. So, except for "limit her future relationship to a single man", is there any other thing she can do?