What did the DB coach tell you about how to address the affair? Your W is engaging in "cake eating", she's living her "married with children" life while also actively engaging in an affair. Personally I think you should let her know you're aware of the A so that you can set some boundaries. I'm not saying get in a big fight about it, rather I'm saying sit down with her and calmly disclose that you know what she's been up to and lay out whatever your boundaries are, then give her a timeframe to decide what she wants to do.
