Breathesgirl, thank you for your suggestion - it's a good one! I write most of my thoughts and emotions down and find it as helpful as you describe it. If I didn't do it I'd probably just explode. But still sometimes I forget about it and it helps to be reminded.
GS, thank you for your advice. You've confirmed many of my own thoughts on the situation and helped me focus.
Unfortunately our situation has gotten worse, or maybe we just can see it more clearly.
Do you think that's what she wants/needs ? Monogamy ?
That's entirely possible. Today she almost broke up with our BF. (I know of all this only from him, as she doesn't want to talk to me at the moment, understandably, when she's in such an emotional uproar.) She didn't do it in the end, apparently she wants to find out more about what she really wants and work on her dependency problems, which she knows can't be solved by changing her relationship form. But she made it clear that it is possible that in the end she still won't be able to be in a poly relationship (or won't want to).
If their relationship ends because of all this, that would be my worst case scenario come true. I love them and I love how they are together.
But I can't do anything more than be there for the two of them.
I can't even back out of my relationship with him in order to save theirs, because that wouldn't do the trick: basically, he would still be poly and she would still be insecure. (Not that I'd want to leave, but it's a theoretical option I'd at least consider if I could actually achieve anything with it.)
It's all a big mess.
I wonder if anyone's ever been in a mess like that and came out with all relationships relatively intact?
Sometimes I'm scared that maybe polyamory just can't work, that there's always someone who suddenly comes out as mono and everything breaks down. This has happened to me twice now. But there must be people who really are poly, right? Because I am, and I'm not that super special.
Sorry for rambling. It's all a bit much right now.