Treading water, for days; no end in sight

It's hard when someone you love deeply undermines their relationship with - 'betrays' would not be too strong a word - someone else you love deeply, and justifies their actions, and lets that relationship stay broken, and doesn't understand how every conflict that happens after that has its roots in that initial violation, and there's no way for you to fix it and no one, really, for you to talk to about it who really gets it. Even putting it in these terms is going to be construed as a violation of trust. (I'd like to say 'misconstrued,' and I think it would be accurate, but violation is usually in the eyes of the violated.)