So, you weren’t promising permanence, but neither was she, expecting the relationship to “expire” at some point, and in the meantime accusing you of being prepared to leave her for another person, even though BY DEFINITION poly means being able to enter a relationship without abandoning an existing one. If she had found someone she’d rather be with, she would have been the one leaving, since “serial monogamy” doesn’t lend itself to multiple concurrent relationships. That’s a bit… well, hypocritical. And it ignores the basic definition of poly in order to use it as a weapon, which I am heartily sick of seeing.
I believe in commitment, I believe it can occur between more than two people at a time, and I also believe that sometimes it is necessary to break a commitment if something goes so horribly wrong that it is hurting the people involved. I’ve known people who stuck with their commitments in spite of the terrible things it was doing to them, and I hope never to experience that in my marriage. I fully intend for this relationship to be “til death do us part” and for us to be good for each other until that time, regardless of who else may or may not be involved in it with us.
Just in case anyone is wanting to make any snap judgments about what poly means to me, I could not possibly get involved intimately (sexually or otherwise) with another person without having real feelings for them and wanting a serious relationship. So no, it doesn’t mean “sleeping around”. It means “being in love with more than one person at a time”, and that itself is something I have no more control over than the fact that I prefer men to women. I did not choose to be poly any more than I chose to be heterosexual. I simply discovered the fact after a lot of living and loving and making mistakes and self-searching. And then found out that there are other people out there who feel similarly, so I didn’t feel quite so alone anymore.