Perhaps the girl got carried away in the moment? Perhaps she was so thrilled that some guy wanted her other than you that she thought she had better reward him? Perhaps she was just plain scared to tell you at the time and took what she mistakenly thought was the easy way out? Perhaps she is really not ready for a relationship of honesty, openness, integrity, respect, dignity and commitment to communication no matter what? Perhaps she just doesn't want to, or can't live up to the task and hard work of being poly (or any relationship for that matter).
Bottom line is though that if she shows no concern or remorse in the light of your rage over this lie she produced then she is not worth your time....
you seem to be seriously considering poly and a healthy relationship.... go get one.
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