I am thinking of Maria Shriver and Arnold Shwarzenegger as a prime example of how some women express complete incredulity at their husband’s choice of mistress.  There they are living together with their 4 children and unbeknowst to her, he is having a liaison with their housekeeper which resulted in a child.  Many women in our support groups talk of their husband’s having affairs with their best friends or people who they would never imagine would collude in their husband’s betrayal.  Often the mistress is envious of the marriage and the fact that her friend seems to have it all, the home, a family and a husband.  She can’t bear to be on the outside and would just like to have it for herself.  I suspect that the housekeeper who had an affair with Schwarzenegger was seduced by money, power and a touch of envy of the woman who seemed to have everything.