Re: My wife the liar, how could she do this to me.
Do not cheat! Your wife may have lied, but she did not commit adultery. When your wife slept with those men, she was not married to you and probably didn't even know you. She did not have sex with the intent to hurt you. If you have sex with one of her friends, you'd be committing adultery with the intent to hurt your wife. In my opinion, a far greater sin than having pre-marital sex and lying about it.
By having sex with one of her friends, you would be showing a lack of character, morals, and grace. It would be far from showing forgiveness for your wife's sins, so she should not feel compelled to offer forgiveness to you either.
My husband broke our marriage vows, so in my mind if I wanted to cheat . . I could. My vows are broken. But I am not a vindicative person who wants to hurt others, even those that have hurt me. I do not believe that's the type of person God wants me to be. Betrayal hurts like no other pain I've known, but by giving into it and becoming something ugly is not rising up to the challenges in life. If God wanted you to learn something from this experience, I highly doubt it's "get even" by breaking one the commandments.
I see my husband's betrayal as a way to improve myself and my relationships. I refuse to become a shell of the person I was prior to d-day, if anything I want to be far better. Yes I'm still hurt and of course I have thoughts of "getting even", but that's not the kind of person I was raised to be. My H's affair may have stolen my innocence and ability to trust, but it will not change my moral character.
Think long and hard before you decide to lash out in your hurt and anger. Intent even plays a role in the courts. Take manslaughter vs murder for example, the one with intent is judged and sentenced far more harshly.