Pretty much what Cougar said.
The description in the OP made me think you MUST be writing about a mutual ‘friend’. My wife had the misfortune to get drawn in to the world of perhaps the most passive-aggressive person I’ve ever met.
She is a large girl (mid 30s) and has a very, very loud voice. She dominates conversations and is incredibly sensitive to any suggestion that she is in any way out of order, whilst also being incredibly insesitive towards others. She dishes it out in spadefulls but can’t take any back. At all. As in the OP, she lashes out verbally, sulks and badmouths whomsoever has been unlucky enough to cross her. Every ounce of drama is drawn from every situation.
On the other hand, she can be very thoughtful (rarely), is a great organiser and is good fun in a big group and small doses.
She wormed her way into our group of mates and although everyone feels the same way about her in private, she always jumps on any plans with huge enthusiasm, and no-one wants to tell her to get lost. We often organise holidays and away days in term time to avoid a huge scene (she’s a teacher).
To make it all much worse, it turns out she’s now going out with one of the guys in our social group. Frankly, he’s a bit desperate, but none of us knew he was that desperate 🙁
Feel better for that.
EDIT – meant to say, the guy she’s now seeing is a really gentle, unassuming kind of a guy. Not very socially able but still a decent bloke. All her previous relationships have been car crashes in slow motion, shrouded in secrecy and drama. This new relationship was kept secret from some of us for six months. God knows why, as no-one gives a shit really, apart from feeling sorry for the guy…