M.L.
Yes, I would call block her number. If not, he is going to have to be firm and decide when a good time is in his life to let her back in by maybe meeting for lunch somewhere and discussing the issue calmly. Either way, it is going to take time. It depends greatly on many things in their relationship, if her behavior was suspicious prior and all that. If just a girlfriend with no kids, I wouldn't waste my time on her.
I think it's interesting that, had this been a man with a women in his bed, the answers would mostly be, "the scoundrel!"... but b/c it's a women... other women are coming to her defense with, "Well, there are two sides to every story" or, "She might not have been cheating...". Wow, women cheat too ladies!
If they are going to watch tv.. do it in the living room! I stopped consoling men like that PRE--marriage. Were they under covers, were they snuggling?... seriously.