Should I divorce my wife?

[At Wit's End]

Last month, my wife got into a huge fight with my 13 year old daughter and told her she wished she was dead. My wife has terrible mood swings and can be verbally abusive. She has done this to me quite often throughout our 15 year marriage, but this is the first time she has done this to one of the kids. At about the same time, I found out she was setting up an extramartial encounter with someone she met through the internet. She has admitted to two other affairs during the course of our marriage. I feel guilty about wanting to leave, but I feel enough is enough. What should I do?