She has to go through what she has to go through. You cannot help/ force anything. Be there to listen, validate, etc. BUT she has to heal on her own.
I 2nd this one, Bad. "I'm sorry you're hurting," or "I hate to see you hurting" is a good way to validate her pain, without condoning her affair.
The most important thing is NOT to rescue her from her pain. When my wife would sob behind a closed bedroom door, I would leave her for a good hour, and then tap on the door and ask if she was okay, or maybe then I would go in, hug her strong but briefly, and say something like the above and then leave with a "let me know if you need anything."
