I have reread the thread. I don't think my Mum is a toxic parent
And yet you've said these things:
I am worried that my mother will go ballistic and I don't know how to deal with the emotional blackmail.
She wanted to move in for several months when my baby was born to help take care of her and generally boss me around. My partner pusuaded her to go home after a week as she was stressing me out just by visiting me in hospital.
If we don't go to her this will reinforce her view we are 'keeping her grandchild from her.
Everything is fine if I do what she wants but when I try to put boundaries in place she tells me how much I have upset her and won't let it go until I change my mind.
On the few occasions when I didn't change my mind she still brings it up now how much I upset her.
She bullies you into doing what she wants by "going ballistic", accusing you of keeping her grandchild from her, refusing to respect your boundaries, telling you you've upset her when you try to enforce those boundaries, and banging on about things long-past in order to manipulate you.
She sounds pretty toxic to me. But I do know how hard it can be to acknowledge that, because it throws so many issues into focus--and gives you a lot of work to do.
If you don't want to spend Christmas with herand it sounds as though you'd be right not tothen just tell her. Treat it like it's not a big deal. Don't try to justify your decision, just tell her. If she goes off on one then tell her it's not up for discussion, and refuse to get drawn into a conversation about it. If she then "goes ballistic" tell her you'll not be spoken to like that, and hang up or leave the room.
Treat it like it's no big deal. Don't get drawn into a conflict about it. And most of all, enjoy Christmas with your lovely baby and don't allow your mother's emotional blackmail to cast a shadow over it. It's her problem, not yours.