SIL: advice please

[LandladyofTheValley]

I've been with my DH since I was 18. It's 25 years this year, married for 7, two DCs now teens.
He has 3 DSis all a lot older then me. I've always been incredibly respectful of his family.
They've been ignorant of me for years. They've had days out and holidays where I've been excluded. They've been pretty dismissive of me.
When we've been at family events they have been fine, civil. When DH asked why I'm not invited to things they always had an excuse, like they had invited me but I must not have seen a message or they thought I was busy with the DCs (they are all what my DD refers to as "Trad wives").

When DH and I got married, it's a family tradition for the siblings to all chip in, so DH has paid for things for their weddings without a thought, in fact one of them has been married twice and both times he contributed.
When we got married they offered nothing, no help. I don't have family, so it would've been nice to do the dress and other shopping with them but they made excuses
DH commented on this so one of them said she would arrange make up and hair for my Bridesmaids and me. She then told me a month before that the lady she hired had stopped doing that. As a result I had no one to do either at such short notice. I had no one to help me get ready on the day so DH came home briefly and helped me put my dress on as it was corset backed- my mates live back where I'm from a good 4 hours away so I couldn't ask them.
They made comments about the wedding and reception. They really pissed me off
They were all invited to a 25th anniversary party we hosted. They all declined a week before despite being invited months before - which is usually their excuse as we "didn't give enough notice".
DH got angry and one of them rang him, saying in her view he "could've done better" and she didn't believe he loves me, nor that I make him happy. She called me lazy and fat. He got very annoyed. Told he she is completely out of order. This was why they didn't attend and none of the rest of the extended family çame because they told them it was cancelled!
I want to message her myself but I worry if I do I will start a bloody war.
Is it worth it? I'm proud of DH for sticking up for me but want to do it myself

OP

This toxic dynamic has been going on for years and likely predates you. His sisters see their brother here ie your H as their personal scapegoat for all their inherent ills. They would have likely behaved the same regardless of whom he married.

I wonder what it was like for him growing up with them. Pretty miserable at times I would imagine. It could be that one of his sisters is dominant and the other two go along with her out of wanting a quiet life and not wanting to be a target for her bullying.

The error you have made here is to at all try and include them in your family celebrations like your 25th wedding anniversary. They have shown you by both word and deed repeatedly they are not bothered. Your DH can continue to deal with them but does he want to maintain a relationship with any of his sisters now?. What do his parents think of their daughters' behaviours?.

I would drop the rope and personally have nothing more to do with his side of the family. Not your circus nor monkeys. With you people out of the picture entirely the three of them will hopefully turn against each other.

Don’t message her. Just let her go out of your life. I would not lower myself 🥲

I would not message her because any message you send is a response and that is what is wanted; she knows she has you then. To such disordered of thinking people like described a response is the reward. In addition a response no matter how carefully worded or otherwise will be seen by them as an attack and so will act accordingly. A response also invites communication and this door needs to be closed.

That would be the final straw for me. You deserve better. Cut them off!

It's just difficult not to bite because I've kept quiet for so long. They're definitely trying to cause doubt and it's worked before as their other brother split up with his wife after they made things so awkward and caused a huge divide between them. It resulted in her saying, me or them and he inexplicably choose them. He has been miserable ever since.
I don't believe DH would leave, but I genuinely despise them. Their own relationships are shit but they want to fuck mine over.
I won't react but I won't be attending anything they're at from now on, DD has decided they want no contact going forward due to the behaviour she feels is directed at her and DS is undecided but says he's really angry after hearing the phone call.
If they'd ever bothered to get to know me I would understand if they felt they were making an informed judgement, but they aren't.

Block them on everything and try to forget they even exist. You never have to see them again.