Has your NF belief in the inherent good of other people, screwed you over royally before?

Why, yes. Many and many a time. Similar to what you have described here, and otherwise, variously. For which reason I tell few people what I really think. I think, especially for someone who is as sensitive as to shake and burst blood vessels, you need to be very cautious of who you let in close. If you don't do this voluntarily, time will teach you the hard way; this is my belief. Which is not to say that all people are bad -- but when you reveal a powerful secret about yourself, such as that you might be transgender, it produces a backlash in the other person -- it pushes all sorts of buttons in them -- to some extent, I think they are not entirely responsible for how they act because they could be in the grip of crises of their own produced by the having to step back and look at you again and go through changes in their heads about you, etc. Being very honest, I don't really understand why it is thought to be so great to think that all people are good. They're just not.

So very sorry to hear about this betrayal in your life.

P.S. I usually just doorslam and I mean slam it hard anybody who does me like that (I can only think of 1 person), but probably the farthest I would go is to shock her, like, entertain a very light-hearted conversation with her where I got her all happy and in a fun mood, and then just before I was about to leave, throw out "So, what are you doing for fun now that I've had your fake account on fb shut down?" and watch her wet her pants. While she's stumbling around denying she knows what you're talking about, throw in, "I really liked it when you _______ (whatever she did that was particularly stunning in either its stupidity or cruelty); that told me a lot about who you are," and then "Ok, gotta go, catch you later!" all completely as if nothing is wrong.

But Marmie's suggestions are brilliant, too, if you have the stomach for it, and you might, once you get over the surprise and disbelief that she's even doing this crap -- you might get good and mad enough to do them.