get as much info as you can get a keylogger...listen to what she says when she says dont send her informative emails on affairs...I did the same shirt- shes beyoung logic and morals, she's lying to her H and getting emotional needs met outside the m.
Get as much evidence as possible, do not confront her immediately, build your case, etc etc...if you confront her or when you confront her- do not confront her first...Allen will have more to say on that.
But, when you do confront her, do not disclose your intel...she will manipulate you by lying, downplaying, etc etc...if you NEVER tell her how you know, your sources are safe and you can continue to monitor.
There will be LOTS of lies...dont engage her, walk away-
Again hold off on confronting her...let her know you want the M to work and that you will protect it from OP whom are attacking it.
GAL, be responsible, be detached and MATURE- do NOT BE EMOTIONAL