It's ok to disinherit a firstborn if remarried and have a new family, right?

She’s so angry with your dad that she’s forgotten that you are a separate person. Awful for you. Do whatever feels ok to you at Christmas.

Where are you OP? In Scotland you can't disinherit children.....look up Legal Rights

It is not ok to disinherit you. (If she can legally do this … is another matter.) Your mother sounds very mean and honestly crazy - there is no logic to her reasoning! I feel very sorry for you and I completely understand you feel hurt. But try not to take this too personally … she is in the wrong and none of this is your fault!

I disagree. It’s not about money. To disinherit a child in this way is emotionally toxic. She is punishing the OP and ‘othering’ her. Making her feel less than her step siblings. There are ways of sorting this out that don’t need to be done so meanly. This mother is toxic. The OP shouldn’t chase the money, it will be awful for her, but she shouldn’t try and build relationships- this is down to the bitter mother taking it out on her daughter. She needs to do the work. Not the OP.

Your mother disgust me OP. Better for you if you have nothing to do with someone like her.

So sorry for you OP. It's much more than being disinherited; it's about being disowned. I cannot imagine my parents doing that to me or me doing that to any of my children. It seems she has focused all her bitterness and resentment on you. It's not on you. Perhaps you could write a short letter to her just stating that whether she likes it or not you are her daughter and that you are willing to keep the bond between you alive but will not be in contact until she has addressed her issues and apologised to you. What is your relationship like with your siblings? I'm guessing probably not that close considering your mum's behaviour...

Withdraw from contact for a few weeks; do you have someone else to spend Christmas with or can you arrange it now? It isn't appropriate to blame half siblings for their mother's behaviour, so unless there are other issues just post their cards and gifts today. You would benefit from some counselling to consider what, if any, relationship you want with your mother going forward.

Maybe your attitude to your siblings is off? They’re related to you through your mother - it would be complicated to inherit anyway with your step-dad in the picture.
She’s right you are in line to inherit from your father and you’ve said yourself that you’re independent so try to let it go. Build relationships now without a view as to what you’ll gain financially from them.

No. Nasty. That’s an awful post. Well done for calling it out.

That is shit. Sorry OP. She sounds horrible. I hope you have some good people in your life. Listen to Dr Ramani on growing up with narcissistic parents. I know ‘narc’ gets thrown around a lot but it’s about recognising behavioural patterns (often stemming from difficult childhood relationships) and protecting yourself from getting sucked in to difficult dynamics and looking after your own well-being. Once you see it as a stuck behavioural pattern they can’t change and that it’s not about you, it’s easier (ish) to let go of the hurt. Sending you an unmumsnetty hug from another one with a toxic mother.

Necessary????

To be honest your mum sounds quite emotionally abusive. Seems like she’s somehow punishing you for the wrongs she perceived your father committed against her. Totally understandable that you feel hurt, but you should realise it isn’t really about you or anything you have done. Someone suggested you get therapy - and yes that is a good idea - but the person who really needs therapy is your mum!

Who is the 'we', @Eatcabbage , in the sentence "...we were supposed to be joining them all, including half siblings, after Christmas and I don't think I'll be at all welcome now."
Because if you can get out of it without any fuss, i.e. disappointing children of your own or whatever, you should. I wouldn't, in your case, spend five minutes more of my life on this woman who doesn't deserve you.

Gosh i can't imagine being so full of spite. Sorry OP this must be really hard. I do think you should reflect on whether you want this woman in your life.

you are right , dm is hurting you to get back at df. You had no control over dm choices and I’d ask her why you are getting the fall out from her decision to divorce… and back off from her. your step siblings can provide any support she needs moving forward.

Woah, I didn't realise you were in active contact. Have a look at the Stately Homes threads on here if they're still going. Read up on FOG (fear, obligations and guilt). Get some counselling. Redraw the boundaries and reduce contact. You don't need to continue to pander to your mother, you can redraw your relationship and find peace.

And don't go at Christmas.

I've never heard of a mother disinheriting her children because she paid more than her husband for them growing up. The net effect is that you'll be left less than your siblings which doesn't seem fair. It's not you being iver sensitive. As others have said, it's you being punished for how she feels about your dad's behaviour

You are correct, you can't disinherit your children in Scotland. My MIL tried to, but DH and siblings tracked down the estranged child and made sure they got their share. It was the least they could do after MIL abandoned them.

OP I can understand why you are so hurt. Your 'D'M sounds like a complete narc who will never be done punishing you for your parents' split. You poor thing. Have you thought about counselling?