I know just how you felt, I had that experience a while back, a kind of alienation. I don't know what causes it but I'm sure the stress of dealing with a rollercoaster relationship doesn't help. I think maybe when you make a big decision,like confronting the A's behaviour it can throw a lot of other perceptions out of kilter, even though you may feel empowered.
I found myself feeling quite alone at times, optimistic one day and down the next, and the way you see other people changes. My solution, the only one I know, treat myself well, eat and sleep well and spend time with people I value and I know value me.
Take care.