I was reading your post, and I'm sorry....uh, what were you saying?
Okay, dump them all. In fact, move out of the area, or possibly the state. Change you Cell Phone , your name, your social and get the hell away from these people.
A dates D, breaks up and dates B who lives with E. E reports to D everything that A and B were doing. D and E tell A that B is crazy. B is back, and is she nuts? Hmmmmm?
A-D+B(+E) / (E+D)-B= 3.1408450704225
B is probably the only normal one in this group, everyone including you is sort of whack.