Work on the marriage in counseling (possibly bring up the term there). Once it is solid again, then you can bring polyamory up if it is something you really want to delve into discussing with her.
I get the feeling my wife wants to just forget any of this happened, but like you all said, that's not a good idea. This is a great opportunity for our relationship to grow....
sounds like she's not Poly and just made a mistake.
The other thing... You mentioned you are an introvert discussing this issue with a bunch of strangers. The anonymity of the internet is a strange thing isn't it.