My wife and I don't want this situation with B and C to bring about the end of what could have been an amazing family. Is there some way to use "I" language effectively to defend against somebody whose response to being upset is "I can't control your feelings, only you can do that?" Because, seriously, that's manipulative, projecting, unkind, irresponsible bullshit. Basically, she's all like "well you don't like it, tough, live with it. I get to manipulate you all I want, and you can't feel bad about it."
How do we deal with that?
The woman seems completely unwilling to take responsibility for her actions, her words, or her emotions, and instead painted us into such a crystal clear representation of "the bad guys" that she truly believes it, and she can convince her boyfriend of it, too.