Okay, but curious, though -- isn't that assuming she felt she had to make a choice? Could she not have conceivably just fallen out of love with the other man, and simply chosen a monogamous relationship with someone else?
When you say, "That's not poly", for this situation, I'm not sure I get that. It's definitely unfortunate, but if we could take a look at any set of loving, sexual relationships involving more than two people that, for one circumstance or another dissolves into separate, uninvolved groups (as in this instance, the one man alone and the wife moved on to form a new couple with another)... ...well couldn't that group have been considered poly originally?
I think to say that the relationship CG2K described wasn't poly because we assume the mechanism leading to the results becoming unfavorable was that one somehow felt forced to choose (rather than them deciding of their own accord that it was time for a change and relationship boundaries to be redrawn) may be an argument more protective of the integrity of poly relationships than it is accurate. That is to say, if you can look at a failed set of relationships, and based on an assumption of the mechanics therein, figure a way to declare it "not poly", isn't that a bit of a convenient out in the defense of polys to declare it just "failed monogamy"? I know you can't and don't deny that there are failed poly relationships as well, but isn't this just pushing up the goal line to make it a loss for the other team?
Pardon my clunky phrasing -- not sure if I'm getting my point across, but still look forward to your response. If it's not clear I'll try to make it moreso next time.