It sounds to me like she might be a bit of an NRE junkie. The NRE died down with you and your absence for work didn't help that, and so she found another to have that energy with.
There is nothing wrong with NRE if there is some control over it and all the foundations of poly are at play. For me the foundations are to respect, communicate honestly and openly, have integrity and empathy. It sounds like she was a bit short of empathy and not entirely respectful as a result. It doesn't sound like your feelings weren't considered by her and that you were made to suck it up while she just went ahead and did whatever she wanted... I don't know, as I don't have her story, but that is what it is sounding like from your perspective when she said was more drawn to him because of your hurt and pain.
I don't see why you needed to break up though. I guess if it was all too much then ya, but there might of been room to negotiate your boundaries a bit more and a long conversation with her and him might of achieved some more appropriate boundaries for all of you.
There is no reason you had to give up your once a week and be in her life with less texts etc. You could of requested that when you see her for a weekly date that there only be an hour of conversation about him and the rest be free to talk about other stuff and requested that in order to feel she loves you that she text you once a day... that's the thing with poly, you can work out whatever dynamic works... to me it sounds like you were on the verge of that and then threw the baby out with the bathwater and gave up because it was too hard and you wanted it over... well, it doesn't sound over, because you are still hurting and so is she.
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