Am shock when I read this through, but nevertheless even from the speech of the ladies @oluwatobiloba, the lady heart was still with the guy so much. I could pick this from her speech and I quote her;

I definitely cannot get over him like that, I have never loved another person and he is certainly okay for me, he is everything I want in a man.

So my advice for her is very simple, even while the lady was cross checking the message and chat, the man and the lady have done, she said her man had already told the lady that what happened between them was a mistake. And she even mentioned that he cant betrayed the love he had for you. That show it does not happen intentionally, probably the lady lure your man into that.

So I think the guy deserves second chance, after all he pleaded such would not happen again. Give him the chance and move on with him. Am sure it will end well.