I've had some amazing responses and lots of great advice thank you.
I've banked it all because it's not actually come up since and I'm too much of a chicken to bring it up - not after the week at work I've had 😂
So for those questions -
Yes DH definitely needs therapy. We've had relationship counseling in the past which has been amazing for us and I do know that this is a DH problem, not mine. He is otherwise a great man and a wonderful husband but his mother is like his Achilles heel. I can't forget that he's had 40 years of her mistreatment so it's very hard to undo in one conversation.
Re the honeymoon. Oh my god 😂 we booked it very last minute. It just came up in conversation because WHY wouldn't you share where you're going?!
A week later she reveals very nonchalantly that she's also going on x date and I just remember staring at her dumbfounded because I thought it was a joke.
I later said to DH what the actual fuck - and we agreed to quietly change the booking to another resort and didn't mention it. She took her trip, we didn't talk about it again, she never contacted us during and it was forgotten about. But it was utter batshit - who would do that??
She also turns up at the front door at the most inconvenient of times. Calls on birthdays/anniversaries needing urgent help to pull him away from me. Im pretty certain she breaks quite significant things in the house on purpose (there was a flood once that needed repairs and weeks of decorating at the hands of DH) to get him back in her house.
I am very much the woman who stole her son because she used him as a stand-in husband for many years after his dad left. Even as a young teenager he was paying bills and fixing up the house. When he moved out to live with me years ago she was horrified and made sure he knew it. "You left me, how am I meant to cope on my own" etc etc.
What's worse now is she's been such a manipulative, victim playing bitch to all her friends in recent years that she has none left so we get very little reprieve.
So this woman, I tried for years to build a relationship, did her favors, brought her lunch, suggested hanging out, got her involved with my wedding planning and at every turn she threw it in my face and so now I just don't give two shits what she says or does. I used to tangle myself in knots with anxiety but not any more.
BIL has seen the light of what she's like and we are edging in tiny steps towards DH putting in some boundaries but you can't undo a lifetime of abuse and toxicity in one conversation.
So when it comes up - my plan of action is just to say no. And if he doesn't pick me then that really is a hill for me to die on. But I don't think it'll come to that.