She isn't worth it, is she?

Reading and trying to keep up with the drama was more than enough for me. I had similar behaviour in my high school friendship group, which stayed together for a few years after we left school, and I wish I had left it sooner rather than persisting for even a few years.
If it were me, I wouldn't bother trying to handle it anymore. Leaving my old group felt great, so much less stress and drama which I don't need on top of work, kids and everything else. For the last few years I have kept my close friends and see and talk to them regularly, which is so much better.

This ⬆️

No idea.

"but was I just supposed to allow someone to be horrendous about people without confronting them"

Yes.

She was being ‘horrendous’. That’s on her not you.
You weren’t obliged to listen to her horrendous stories. You could have put a little distance between the two of you, or changed the subject, or made a polite excuse to walk away and determined to give her wide berth in future, all whilst keeping your counsel.
She would have maybe got the message eventually without a big bust up. Especially if A, C and D also had to listen to her being horrendous. Or was being horrendous saved just for you?
If so, a slow fade wouldn’t have been a bad thing for you.

It wasn’t your job to take it upon yourself to suddenly confront her without warning after absorbing all her horrendousness for all those years. She thought she had a partner in crime with you to off-load to. So cut you off the minute she realised she was mistaken and then ran to A to get her story in first.

It’s unfortunate that you lost friend A as a result of your decision to confront her.
Friendships wax and wane…don’t spend too more much time feeling upset and offended by it all. These little injustices are all part of life.

It's really bad form to post links to OP's other threads, and in the old days of MN your posts would get deleted and you'd have been piled on @denimstork8

OP, I think you need to accept that you've lost the friendship of A, but from what you've written on this thread, that's no loss.

Grown women behaving like nursery ages children!

@RedIvy18 sounds like B has got in A's ear! being fake best friends now I presume? hopefully, B will show her true colours soon to A and A will open her eyes and realise that you arent the baddie in all this/

This.

I also dont think there was anything wrong in offering to stay away from the party yourself.

It was clearly an attempt to diffuse the situation which backfired. But you couldn't have known that would happen in advance. B clearly decided to dig her heels in and make an unnecessary point. There was nothing you could have done at that stage.

Except perhaps not offered in the first place and then just let B refuse to go but then someone would think you should have offered to stay away and let your husband take the kids and accuse you of creating drama anyway!

Unfortunately, there are those who pander to difficult personalities and tolerate poor behaviour and those who don't. Those who consider woman standing up for themselves as others as troublesome and those who think it's necessary.

They rarely make for comfortable bedfellows.

Keep your friendships with C and D safe from this by not discussing it with them (no one wants to feel caught in the middle).

A may well come to regret her decision one day.

It’s bad form to keep posting the same thread multiple times.

You also seem to vary the details in each one (e.g. sending DH to the party) so no one knows what’s true and what’s made up).

If you have so many friends why are you so fixated on 2 people who don’t have much do do with you anymore?

If A and B are both out of your life it’s time to put this to bed.

Mumsnet: don't be spineless, call people out on their bad behaviour or you're complicit if they're slagging people off

Mumsnet on this thread: you should have just listened to her bitch about mutual friends, why did you call her out, no one likes drama, you are as bad as her. There must be stuff you've not told us

Going on this thread, you've not done anything wrong. B sounded horrible. It sounded like you told her multiple times that you didn't like what she was saying and she didn't listen, so you had to tell her in a different way.

It was probably naive though to think your friendship group would be unaffected. A has clearly taken sides which is a shit thing to do without at least hearing you out. So she wasn't a good friend after all

Have C or D ever spoken to her about it?

I can see it’s the same people. Ultimately you wanted to distance yourself from someone who was being nasty a lot of the time and now you have. For your other friends it’s up to them what they do or how they handle the situation. If they want to stay friends with everyone and see people separately or prefer to no longer be friends with you or the person you’ve cut ties with they can do that too.
I can not in a million years envisage a situation where I (or one of my friends) would refuse to go to an event because another person was there and tell the organiser. If I really felt that strongly about not seeing someone I’d politely decline the invite with an excuse. On the whole it’s best to let the friendship go and work on cultivating other ones. In future it’s probably also better to just see someone less/do less with them/not tell them anything confidential if you don’t like or trust them.

OP you sound totally reasonable and this thread is sadly full of arseholes who love sticking the knife in. Ignore them. In reality you did nothing wrong.

If someone is being nasty to other people then one of the consequences is they may have to deal with people telling them so. If they don't like it, we'll they shouldn't treat people so badly and expect you to be a party to it.

Although it's difficult letting go after all this time, it's likely B has poisoned A against you.

Time to move on.

This all sounds so exhausting!
move on.