[yasuohate1]

I'm struggling to see how this is an extra marital affair in any way. There's no sex, no flirting, no mention of time spent away from family, just alot of constant coaching (as what a superior should do).

The only thing that remotely points to any flirting on the guys part is that he finds ways to get her attention but even this is not substantiated.

Perhaps there is something we are not seeing or maybe you haven't shared clearly. But like what other bros say, I suspect your friend might be reading too much into it and she might have had a crush on her boss.