I always wondered if I could forgive a betrayal and supposed I wouldn't. But I think it depends on the person close to you. How strong are your feelings towards each other?
In this case the affair lasted for 6 months - quite a long span of time. As I concluded from the reason of the proceeding affair, the girl lacked attention, her husband's ability to listen to her dreams. But these are the main things we seek in our partners and he couldn't provide them! I guess the event will reiterate. The spouse's forgiven, but has he found out the reason? He should do it and change the attitude to his wife. If no, the alliance will fail.