Marry me instead. Haha.
In all seriousness however, what I’m going to say will more than likely inflame others.
What do you want to do ? Do you really want to divorce ?
How much are you prepared to work on your marriage to this woman ?
Is your partner's lack of sexual or emotionally flirtatious monogamy a real deal breaker for your marriage and the commitment that you once made to each other ?
You have vented on here, rather than choosing to openly communicate with your wife. Clearly then there is a breakdown between the two of you that needs addressing.
You have also chosen rather swiftly I will add to mention the expensive and dreaded D word (divorce) there, has things been bad ? Has this issue merely given you an exit excuse?
Be honest with yourself, your situation, and your partner.
What is it that you want? Where do you want to go from here?
Can things be fixed?
Do you still love her?
Is this a temporary blimp in the life radar?
Can you work or get past it?
After years of marriage, do you both still desire the aspect of monogamy?
I’m a monogamous individual, but it doesn’t work for everyone.
If you look back in history, some marriages that have lasted the lifetimes between two individuals only worked because both parties had their additional chamber lovers.
What is it that you want? What does she want?
Where do you go from here as a couple?
What is then best for your child, well clearly that is for her to see both parents getting along well, without fighting and stressful interactions.
It is not simply about what your wife might have done, but also HOW you both choose to deal with it from here on in.
Just saying.