Okay now I understand a little better, although A's overall decision to withdraw from you remains a mystery to, well, you and me (and others I'm sure). Really sorry that happened, man. That really sucks. Don't suppose there's any chance this could be some kind of an epic miscommunication on her part? Maybe something's going on with her that she alone knows about?
I suppose that at first glance it looks like she simply decided that polyamory was wrong (or at least wrong for her, or for her and J), and that she would just stop practicing it. So she's not speaking to you at all? No emails, nothing?
Gosh I don't know what to advise. If she's not talking to you, and this radio silence of hers has been going on for a long time, then it kind of puts you in a crappy position. How long are you supposed to put your life on hold waiting for her to answer you? I guess the only logical move here is to try to detox from the whole thing and move on. If she wants to rescue her relationship with you, she'd better get right on it.
I hope you'll be able to find some peace at the end of this long gloomy tunnel. I know I can't help much beyond lending a listening ear, but I'll always be willing to do that.
With many sympathies,
Love means never having to say, "Put down that meat cleaver!"