Well put and astute, Yzen!

Bluebicycle, I swear, if it wasn't for gender and age, you could SO be talking about my coworker! It drives me up a wall. Nobody else ever does anything right. (That's amazing isn't it? I mean, what are the odds?! Lol.) It's downright acrobatic how the most innocuous utterance can be twisted to make a put down or personal invalidation. How many sentences per day must begin with "No...<insert here anything which can be translated to "you are wrong">? Also, everyone takes (and "hides") her stuff all the time(!) Oddly enough, virtually every time it is wherever she tossed it last in her pile of crap (aka total chaos work area). It's ALWAYS someone else. (And blame must ALWAYS be assigned, even pre-emptively(!)). Passive/aggressive out the yingyang. I won't even get into her desperate need to make sure everyone knows what she's doing, going to do and going to do after that, and yes, that includes use of the bathroom. TMI. And repeats virtually everything. No sooner does the sentence finish than it is followed with, "as I said" and repeated. She endlessly *****es about the boss and how he does things. All while playing the long-suffering saint. You get the picture.
(For a picture of me, see Edvard Munch's The Scream. Lol.)

I agree with Yzen that the best approach when possible is to ignore. Don't engage if you can help it. Over time I learned to stop and think before I spoke. It was hardest to resist the urge to be helpful. One shouldn't have to stop that impulse!! But after the thousandth time of getting insulted over it, one learns. Quite recently, I got brave and said, "I'm not comfortable with hearing (boss) talked about behind his back." Didn't stop her of course, but at least I've clearly stated why I won't be engaging in any way when she does it. This is a VERY small company, so avoiding is simply not possible. So the next level is to think in terms of damage control. What shields YOU. Like with the helping issue, my mantra is, "don't hand 'em ammo".

My being the unsociable weirdo there has a benefit -- people really aren't surprised that I'm disengaged(!) I rarely talk, and live inside my head. Trick is to try to not let them live inside your head. Not easy!! But maybe think in terms of real estate. Don't let them live in your head for free.

Wow, this is long! Basically... *Ignore *Do not engage unneccesarily (but when must, keep it short and sweet). *Don't hand ammo over. *Don't try to play their game. These folks see only in terms of win/lose (win/win does not compute), and they will do anything to "win". The only way to actually win is not to play. *Try not to demonize. They've clearly got issues. We're not going to be able to change that, so our time is best spent attending to our own needs.

Good luck! I totally sympathize!