Good for her getting into therapy both as a couple and individual. I do hope that they can work things out.
As some other PP have said, I'm not sure there is much for you to do... other than make it clear to her that you're there for whatever support she needs. Remind her through different outlets (text, phone, facebook msg) that if she ever needs to vent that you'll be a listening ear. Or if she needs a night away for some space that you'll gladly get dinner.
I also agree that an emotional affiar is probably worse than a physical one, and it is a big deal. Flame me all you want, but I had an emotional affair while married without realizing it. Once I realized what was going on, it was too late, although I was check out from my marriage anyways, and completely in love with my best friend. I can't imgine how it would feel on the other end, to know your spouse has found a rock in someone other than you, and that someone else is their everything.
Try to put yourself in her shoes a little, and be there for her in whatever way you can.