To rip MIL a new one?

Your first message asks "how can I get through to MIL?" but you've tried, and I think it's time to stop trying.

You can either go NC as many here have suggested, or LC if that's more workable. And if LC is more useful - because it doesn't allow anyone to revel in the drama of you having cut them off - combine that with grey rock and talk not very much about not very much (basically talk about things in your life that are of no consequence, so avoiding all the things that are important to you), and there will be very little for either your mother or MIL to feed on.

It took me a while to work out, but stepping away from the drama and refusing to play any part in it is the best kind of self-preservation...no need for big announcements, just walk quietly away and leave them to wonder where you have gone.

No need to go ripping anything, although that might feel somewhat satisfactory. It will only give your MIL and mother something to bitch about.

Stony silence from you and a succinct explanation for your absence from your DH is the best response.

I think you and DP should just cut contact with both of them for a while, at least with MIL if can't fully cut tired with DM due to family. DP needs to tell DMil sorry we love you, would love to see you for out usual ore-Christmas catch up but unfortunately we can't as you refuse to keep out private information private and listen to our wishes re DM. We can't meet with you and talk to you as you will share information. I would suggest going no contact with her for a few weeks and then revisit if she is apologetic, hopefully this will make her realise you and DP take thos issue seriously.

I can't understand why you don't dislike MiL. She is treating you and your DFiance dreadfully.

She needs to feel the consequences of this, definitely. Then it is up to her if she sees the error of her ways and reforms (unlikely) or you sadly have to reduce contact and the feed of information, so she has no privileges to abuse any more.

Your DFiance sadly needs to be able to say to her:
"Mum, you have shown us you cannot be trusted to respect our wishes re toxic mother, therefore we have to stop sharing our news with you/cut down visits/etc. You have given us no choice."

Maybe tell MIL that she can have a relationship with you or your mother but not both? At the moment she seems to be choosing your mother but would she do so if the choice was very clear cut?

She is being horrible to you by the way. She’s been told you don’t want contact with your mother and it’s upsetting and she’s doing it still. That’s horrible behaviour. There’s no good reason for her to be in contact, not one. I can only think she’s doing it because it upsets you.

I would send her one text ‘if you are going to have contact with my mother, then we (or I if DH wants low contact) can’t have contact with you’. Then don’t see her, no Christmas etc. hopefully she will come to her senses but I probably wouldn’t trust her again,

I’m NC with my mother, and initially had a very hard time making my MIL understand this (I don’t get on with her anyway, and she’s from a very matriarchal culture where mothers walk on water). Both she and my SIL were constantly asking me how my mother was etc, and it’s taken me a good while to make them realise that all mothers are not good ones. They’ve finally got the message.

In your case, I’d go NC with the future MIL. She’s being unbelievably intrusive by contacting your mother, as well as disrespectful.

Yes, best not to go. Visiting her as normal will just give her the green light to continue.

Also tell DH that he is not to tell his mum anything about you as she clearly can't be trusted to keep it to herself.

If you go in all guns blazing you are handing MIL and (not soD) M ammunition OP. It will strengthen whatever messed up bond they have going on, both can claim how unreasonable you are, how you overreact, how your childhood was not that bad but you explode at every little thing. Cut contact with both women and if you have to let some family relationships drift away then that is sad, but necessary, to protect yourself.

I wonder if your future MIL thought you weren't behaving as she thought you should so she'd try and get your own DM to talk you round. She really couldn't have made a worse choice, now you won't be speaking to either of them.

You can cut your mother out. Other family members are controlling you if you are staying in touch with them because of your mother. Losing them might be the price you pay to get away from your mother. They can make their own choices too. You or her.

My now ex MIL told my mother stuff and sided with her. I'd not had a relationship with my mother since I was very young. I was so hurt and upset and MIL had used her last chance with me.

I will never speak to my mother again and I'm moving soon so probably won't see my MIL again after that.

Edited to ask - why don't you want to fall out with you future MIL? She's not someone to trust, or worth having a relationship with. If you're trying for your fiancés sake then he has choices to make too.

I'm sorry, this really is terrible behaviour on her part. I agree, you need to cut contact with her to the absolute minimum. I am not sure that I would even bother to explain further what the history is, it is exhausting for you to do so and if she really cared then she would have listened to you already.

Agree with other posters - stop talking to, communicating with and seeing your MIL
Then she will have nothing to tell your mother.
It sounds like your DP has your back, but make sure he doesn't weaken and tell your MIL anything either.
If you're planning to have children, imagine how back this interference will be then - you need to put a huge distance between you and your MIL now
And don't tell them anything more about your wedding
Good luck!

This

It may just be unfortunate wording but ripping someone a new one is suggestive of causing additional drama.
I have experience of both toxic mil and difficulties with my own mother - different to your experience but some parallels.
I invested a lot of focus into reducing the drama and in latter years commented to dh that not only was I not playing the ‘game’ with mil I had left the game long ago.

in your position I would be extremely low contact with mil (no need to keep explaining, she knows but she doesn’t care really). Short, low key visits, occasional not regular. Be mindful of your social media make sure she can’t get info from there.

Unbelievable that the MIL has got herself into the situation where she can't see her son getting married. I hope the chats with your mother are worth it! Madness. You are doing the right thing not telling either of them .

I think what you have to remember is that you can only control your own actions, not hers.

So, you don’t want her to tell your mother anything about you (understandably!). While you can ask her not to, you can’t force her not to. So you don’t give her any information which she can then pass on. Probably means you have to stop seeing her. This may or may not make her realise that she needs to stop passing information to your mother.

Agree with pp. I had a very difficult relationship with my DM and went NC. A dear friend kept relaying information to her dm who then passed it onto my dm who then used that info to try and reconnect. I tried to tell friend over and over but she couldn't help herself so I had to cut her off too for my own sanity.

Tell MIL she has two choices, cut contact with your mother or you.

I would consider cancelling Christmas and telling her that if she loves your mum so much she can go and hang out with her.

What an infuriating situation. I agree that you should call off the Christmas visit and make sure to tell her why.

I agree with pp.
Sto visiting her.

She's not going to stop what she's doing so all you can do is protect yourself.

As others have said, don’t go off on one- although I fully understand why you feel like it- cut contact with your MIL way down so she’s got nothing to share with your mother. It’s a reap what you sow scenario. She has literally no one to blame but herself if stop socialising with her and don’t tell her stuff anymore. It’s the only way some people will learn. She sounds like a massive shit stirrer, can’t stand people like that.

I think you and your fiance need to make the position much, much clearer. If your fiance is saying things like "she doesn't really get along with her mother", your MIL probably thinks you've just had a typical mother/daughter tiff. You both need to tell her that there could be very serious consequences if she doesn't stop. This isn't a game and if she continues you will have to go low contact with her too.