People get hurt by all sorts of things that they shouldn't. I know I've been wierdly jealous of guys _I_ broke up with, once they find someone new. I don't want them back....but I guess I feel that if their new relationship is working out, they must be doing something different. Trying harder. Fixing whatever went wrong with us. I have NO reason to know that, she may just have a higher bullshit threshold than I did. But the selfish little voice in my head tells me they're doing it better this time, and I want to know what makes her more worth trying to hold onto than me. Nonsense, but it's how it occurs to me. I feel less adequate than the person they're having a successful relationship (or so I guess) with, and that hurts. But I know that just because I'm hurting, it doesn't mean I've got anything to get angry about. At least, not productively. I'm angry at the person they used to be, or even the person I used to be. It's got nothing to do with who they are now, or whom they're with. So I take a deep breath, wish them all the best, and get on with being happy with where I am now.
Still, it's a human thing...when we hurt, we want to be angry. We want to blame the hurt on someone, because if it's someone's fault....just maybe they can make it stop. We never seem to want to admit that pain just happens, there isn't always someone to blaim, and that if you quit fighting it...it gets better faster. Don't know why.
I'm guessing that part of this is what has your exwife in a spin. Your relationship didn't work out...for whatever reason. You're happy now, it's not with her, on some level she can read that as a personal inadequacy. It hurts, she wants to blame someone....and humans can make up the most astounding reasons to justify something they need to be true. All you can do is not let her fantasies become contagious, keep them at arm's length and get on with your life. Ain't easy. Ain't anything LIKE easy. But it's necessary to build that mental wall between her noise and your reality. It sounds like you're doing it right, don't rise to the bait, don't try to shout her down, just drone her out and get on with it.
But as a child of a few divorces (trust me, it was more than one), can I just say that you may be dealing with some crossed wires with your kid(s? don't know if you're still involved with the step-children, or just your natural one). It's sometimes hard for kids to let the new woman in, and still feel like they're being faithful to Mom. Especially when Mom's so obviously upset. She says they can't stand your new girl...and they may be saying things to her that, rightly or wrongly, she can interpret that way. They may even be feeling a little torn about the situation, therefore confused or unsafe, and that gets us right back to wanting to be angry. While I'm sure there's no real trauma, it's ALWAYS a good idea to talk it out with your kids...make sure they know that no-one's trying to replace their Mom, and that they aren't being asked to take sides. Ever. Even if they already know it, sometimes it's good to shore up the knowledge. Just because they're telling you they're ok with it, doesn't mean they're not telling her what she wants to hear too. Us kids get real wrapped up in pleasing our parents when they get divorced, sometimes. We grow out of it (hardcore

, rebellion is a real kick in the chops sometimes).....but especially at the beginning, I know we made it harder than it had to be on ourselves by trying to keep everyone happy. Just a random thought.
All together though, I'm just wishing you peace....time smooths all the rough parts out, you just have to hang in there. Hope it gets better soon.