ooookay, he's cheating? Ya, I would be very concerned and would probably react the same way. You girlfriend needs to read on here about the disasters that have occurred when someone has cheated I think.
Really the whole foundation of a relationship is in jeopardy when someone is cheating or is with a cheater. Essentially she is also cheating and causing a world of pain and suffering on another person, not only you, but his wife. She is ruining her integrity, and degrading the relationship she has with you. Yup, I'd be furious and probably move out into the spare room too.
Good for you sucking it up so far. I can see that you are trying your hardest to let it play out and let her learn from her own mistakes. To what end though? How long and how far are you willing to stay in this? Eventually it will reflect on your integrity and good judgment also.
This is not poly, this is cheating. I see no love in this at this point, just sex and selfishness.
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