NC as posting history combined with this may out me.
My best friend and I work in the same small and highly connected industry in similar roles. There is little to no professional competition between us as we both have particular skill sets that are complementary.
A few years ago my friend had an affair with a married man at work. He had children and I made my views clear that I did not support these actions. I did however listen and tried to steer her away from him, which didn't work. She never wanted him to leave his family - she enjoyed the sex and the subterfuge. She affair has never come out and it only stopped because he moved away.
Since then she's had a relationship with another attached man and in recent months has shared with me her glee that two further married colleagues have