IF your wife actually felt shame or guilt that would be progress. Normal emotionally healthy persons that behave shamefully SHOULD feel ashamed and guilty. Your "guilt inducing words" will have absolutely no impact or shaming effect on her whatsoever TODAY. She may FEIGN upset and call you judgmental or whatever but that's just a good defense to actually having to answer any questions or demonstrate any actual concern about your son.
However, later on if and when she hopefully starts to realize the enormity of her mistake and begins to feel the inkling of remorse, guilt and regret, the fact that you warned her and TRIED to hold her accountable actually scores you brownie points. She may then come to realize that you knew all along what was actually going on (way wards think they've cornered the market on love and life and you just don't understand what REAL living is all about and if you did love them like you say you do...you'd just be happy for them and leave)...yet you didn't. You still stood by her willing to forgive and actually tried to hold her accountable in the face of her wayward wrath which she may then, as a repentant former wayward wife come to understand as testament to how much you actually "cherish"/"cherished" her.
Also...SHE opened this can of worms and asked for it by trying to act all like she gives two turds about how you son is handling the situation. Her disrespectfully ACTING like a concerned parent is a transparent manipulative guise to her primary concern...her affair partner. You being around maybe makes her feel bad about herself so she's pushing for a resolution to alleviate her pain. Maybe OM doesn't like the current situation. She's a selfish entitled wayward right now. Your son is a possession to her and little else while she is consumed by her insidious affair.
If you don't recover. This email means nothing. Send it and be done with it. Your wasting time that could be better spent GAL'ing.
Your call. I'm not emotionally attached to anything you do or don't do. You won't hurt my feelings either way.
The internet is 90% complaining and entitlement and I hate it because I deserve better!