Maybe she was trying to fill a void in her relationship. Or seeking revenge on a philandering husband. Those are just two of the most oft-cited reasons a woman in a committed relationship may end up doing something as controversial as it is common: getting involved emotionally and/or physically with someone other than your spouse.
Women Confess What Really Drove Them To Cheat On Their Spouses | The Stir
Why These Women Cheated On Their Spouses