From my point of view she should be damn happy not to be out on her ass already. Not only has she lied to you but she has put your physical health at risk. Who knows who else the men she has been having sex with have been involved with themselves. Who knows if safe sex was practiced and who would trust her even if she says she did.
Counselling....as a couple to see if your marriage can be saved and for her individually to see what is the cause of her deceptive tendencies.
You caught her and she is looking for a way to salvage either your marriage or the babysitting service you provide. Of course she would claim poly as a defense, but for the most part it sounds like she is engaging in one night stands. I thought poly included a meaningful connection besides the connection of penis and vagina?
Take care my friend. You are a strong and caring person it seems. I hope you find a way to achieve what makes you both healthy but don't let yourself be walked over for the sake of kids, family stability or anything else external. Do it for yourself.
Playing the Game of Life with Monopoly rules.
Monogamy might just be in my genes
Poly Events All Over