Am I overreacting to my wife’s internet history discovery

Just discovered that my wife had some sort of sentimental affair with her 20 years older boss, after confronting her she said, I quote, "I only cheated sentimentally and it was only one sided in my head, he was just being polite"… All this, after two years our relationship went really down from her distancing slowly from me, now I admit I made mistakes and was annoying and we were arguing and all, but this wasn't fair and I think our trust is broken forever, and I suspect there was more to it than she admits

In addition, she seems to take no accountability and is fine with divorcing..

Am I overreacting