Your friend is admirable for being strong in this ordeal. I don't know the details, but in most cases, I consider the one who cheated at fault. Divorce is already available in a lot of countries, and if one is already thinking of cheating, then have the decency to break it up before doing so. As a friend, it is good that you are supporting her through this.
I tend to agree, she's handling it well (outwardly at least) and I also agree about the divorce comment. Not happy? Leave, get divorced. That's not an easy situation either, but it's better than the hurt an extramarital affair causes.