I haven't commented here because I myself am still working through the aftermath of my H's A, and I'm seeing things through that lens and can't be objective. I didn't get the affair vibe...I got more the " validation " vibe, like her actions were desperately screaming for attention/objectification. I think she is very hurt underneath, as if B50 had an affair.
Maybe those nudes you did, whenever they were, have stayed with her, only to really hit during a period of vulnerability, like the menopausal state.