Not necessarily, I was unhappy in a marriage and found myself cheating so I left and found the one I wanted to be with. I have never cheated in 20+ years. In this case she left for an alcoholic, first mistake, and a cheater which indicates compulsive behavior. If she checked his internet log she probably has a sex addict as well. Men and women can seldom be friends without sex becoming an issue. She needs to draw the line or get out before she invest her life into another bad relationship. So grace I disagree with the once a cheater always a cheater but in this case I agree.