What would you do?

My friend and I went out for dinner last night to catch up on life. It has been awhile since we got together. Last night, she shared with me that she wants to divorce her husband. I was shocked because I thought her and her husband marriage is going fine. Her reason is that she is in love with another man and she has been seeing him for months. I asked her has she slept with him and she said yes. Her husband is also a close friend of mine since high school.

Should I say something or keep my mouth?