Should I get a divorce if my spouse is cheating on me with her best friend?

Only you can truly say a divorce is best for you after finding out your spouse cheated on you with your best friend, no one else can make the decision for you. I know you feel betrayed because two of the most important people in your life have done the unthinkable.

If your desire is to save your marriage, I urge you to do so. Do not let your emotions determine what happens to your marriage.

But if you have made up your mind that a divorce is what you need, you will fare better during the process if you do not allow your emotions to guide your decisions.

Not necessarily. You must get to a point where you can discuss the events calmly with your partner, despite your natural upset. You need to find what prompted the affair and whether it was a momentary impulse that got out of hand, like an unexpected seduction from a more prestigious person, or whether there is such a gap in satisifaction in your marriage that your partner is seeking what s/he needs emotionally or physically elsewhere.

Alternatively, is cheating part of your partner's personality - an excitement from acting like this? These matters will inform you whether the marriage can be salvaged with work on both sides, or whether divorce would be the best answer.