I also became the object that BM projected any dissatisfaction or anger that she felt in her life on me (and she has a documented anger problem so that' alot!).
Anything wrong in her life with her living situation or her current husband, or her kids, she would channel it so that it vented on me.
Once she moved I could no longer be the object that she vented on. When my SD came back for her first visit she was talking about how she was fighting with their neighbors. I guess she found a new object.
As long as she has an object that she can focus all her rage at, then she will never have to look at her deficiancies or the mess she created. It in essence keeps her (in her mind) from being responsible for anything. It's always someone else that is causing her unhappiness.
Somehow this last summer (one year post move) I was able to let go of my anger toward her. I always knew in my head that my anger was only hurting me, but last summer I guess I started focussing on my life more closely (perhaps I had been projecting some of my life issues also) and could release it.
I feel free at last (after about 6 years of constant turmoil).
I wish you luck and that your case will resolve itself soon. I think we have lived through some similar battles. I will be thinking of you.