@sunil12a,
Sun, the question I think is why did she feel that she needed to have an affair did you ask her? I am glad that she is seeking help because it means that she feels some what, in a bit of a mess with herself.
I often wonder. If someone cheats, why if it's a once off, not because they are a cheater on-going within their lives.
What is missing? Why did it happen and what can you both do about that to bring it back to where it was at the beginning. She will be asked these questions I am sure so perhaps you can ask yourself the same.. I think if people communicate better then they can always talk. When they stop talking, things go pear shape.
Best wishes