Well, if we'd caught her in a lie in the first month, we wouldn't have stayed with her at that point. But we were already in pretty far, and the circumstances involving that first lie were... unique. She had some confrontation issues, and was scared we'd be angry. What she failed to realize was that lying also caused anger, and worse, distrust.
But we knew she had a history of abusive relationships, so we were trying to work with her. If she'd cheated, or if she'd lied before we ever lived together, well... that would've been the end of it. We took our commitment to her very seriously. Unfortunately, she wasn't capable of the same.
We are better off without her. We loved her and wanted it to work, and it was devastating when it didn't - which was why after she moved out, we decided to try dating again. It was sort of a trial separation, I suppose. It just didn't work. The dynamic changed for the two of them... while she and I got closer, the two of them got further apart.
In all honesty, I think she needs time alone and in therapy, and then she may need to try to be in a relationship with someone who isn't closed off to poly, but is willing to be monogamous at first. She doesn't have the coping skills to handle one relationship, let alone be in a relationship where there are four distinctive relationships at play.
As for us, we had always agreed this foray into poly was a one-time thing. While I still believe (as does he) that poly can work for the right parties, it was never second nature for me... and he readily admitted he could only handle it because I was with a woman and not another man (and yes, he acknowledged this was a double standard). It didn't really matter because I have zero interest in being with any other men. While I loved having a girlfriend (she was the first woman I had a romantic involvement with), I do not ever want to share my husband again. It is challenging and can be painful. Even when I experienced happiness for them, there were times it was tinged with pain. Going into the relationship, I had no idea what sharing would be like. Now I know, and I recognize that it is not something that comes easily or without an emotional price tag.
Given the strength of my bond with my husband, it is hurt I do not need to open myself up to again. Not only from the perspective of "sharing is hard," but also because of how hurt I have been by her. It doesn't matter that I don't believe she ever intended to hurt me (or him). She did, and she did it many times. I am already loved more deeply than I ever imagined possible, and he is everything I've ever needed.