Good evening Srikanth,
First and foremost, I think it's nice that you want to help your friend. I don't know if this will help, but I think it would be useful.
See Srikanth, you must be knowing in today's world each and every one of us is vulnerable to the passions and desires which are forbidden. Everyone makes mistakes; none of us is without fault. Each of us has a past; none of us is perfect. You first said that she was a good girl, right? So then she must have surely made your friend happy and gave him a reason for living. If he was dedicatedly in love with her, then surely he felt very good with her. In today's world, nobody makes a sacrifice for anybody; it's always a give and take situation wherein both derive pleasure and happiness from a relationship.
Now tell me Srikanth, if that's the case, why dwell or only think about the bad parts of a relationship and how bad one is? Why not think about the good one has derived from a relationship which was mutual?
Remember one thing Srikanth, if your friend really loved her, he would accept her as she is with her past if he is sure his love is strong enough to make her change. But if in case he does want to move on, why not just think of the happy moments, lock it in the diary of memories as a good instance?
I'm not saying the memories will not come, but my question is why run away from them? Let them flow and pass on. Life goes on. If your friend has reached so far as an HR Executive, then he must have had a focused goal in mind, right? Despite him loving this girl on the sidelines, then surely he will have the courage to pick himself up and move on. A phoenix, Srikanth, is a bird who burns himself up but again grows out of the ashes. It's up to us also to pick ourselves up and fly high but yet keep in mind the experiences in order to help us in our journey called life.
No one said life was easy. Hey, it's how we look at it. The way I see it, that girl has just taught your friend how to keep his eyes open and be more observant, not look at everything in black and white. So she has done him a favor, right?
Tell your friend this, if he has any questions, he can always let me know. If you have any questions on anything I've written, you can ask me.
Hey, you're given a noble thing to do. Make the best of that, don't lose courage. Instead, fill your friend up with so much positivity that he forgets to be negative. And I hope your friend has actually seen the proof of her being unfaithful and not just relied on people's words. You're innocent until proven guilty, remember?
All the Best!
Aveena