Hi extracrunchy,
re your comment:-
Had a text from mum this morning:
"Do u want lunch to sort out row? Xx"
I don't and I won't, but it's the first time she's acknowledged an issue and offered to address it. Thing is, it's a lot more than a "row" and it won't be sorted out because she is who she is.
Exactly.
Also your DS does not need a toxic grandmother. She has not changed since she was herself a child.
As Cog states you need to state I'll check my diary and leave it at that. Do not make any further overtures. If you were to meet your mother (and thankfully you will not) it will be her having a right old go at you the whole time. These people are completely without empathy for others, she is not interested in you or anyone else for that matter. All that matters to her is her own self and her own needs being met by you.
It's very hard to have a simple, uncomplicated good time with a narcissist. Except for odd spells of heady euphoria unrelated to anything you can see, their affective range is mediocre-fake-normal to hell-on-Earth. They will sometimes lie low and be quiet, actually passive and dependent -- this is as good as it gets with narcissists. They are incapable of loving conduct towards anyone or anything, so they do not have the capacity for simple pleasure, beyond the satisfaction of bodily needs.
There is only one way to please a narcissist (and it won't please you): that is to indulge their every whim, cater to their tiniest impulses, bend to their views on every little thing. There's only one way to get decent treatment from narcissists: keep your distance. They can be pretty nice, even charming, flirtatious, and seductive, to strangers, and will flatter you shamelessly if they want something from you. When you attempt to get close to them in a normal way, they feel you are putting emotional pressure on them and they withdraw because you're too demanding. They can be positively fawning and solicitous as long as they're afraid of you, which is not most people's idea of a real fun relationship.
As for her "offer of lunch":-
Run for cover when they start acting normal, maybe expressing a becoming self-doubt or even acknowledging some little fault of their own, such as saying they now realize that they haven't treated you right or that they took advantage of you before. They're just softening you up for something really nasty. These people are geniuses of "Come closer so I can slap you." Except that's not the way they think about it, if they think about it no, they're thinking, "Well, maybe you do really care about me, and, if you really care about me, then maybe you'll help me with this," only by "help" they mean do the whole thing, take total responsibility for it, including protecting and defending them and cleaning up the mess they've already made of it (which they will neglect to fill you in on because they haven't really been paying attention, have they, so how would they know??). They will not have considered for one second how much of your time it will take, how much trouble it may get you into in their behalf, that they will owe you BIG for this no, you're just going to do it all out of the goodness of your heart, which they are delighted to exploit yet again, and your virtue will be its own reward: it's supposed to just tickle you pink to be offered this generous opportunity of showing how much you love them and/or how lucky you are to be the servant of such a luminous personage. No lie they think other people do stuff for the same reason they do: to show off, to perform for an audience. That's one of the reasons they make outrageous demands, put you on the spot and create scenes in public: they're being generous they're trying to share the spotlight with you by giving you the chance to show off how absolutely stunningly devoted-to-them you are. It means that they love you; that's why they're hurt and bewildered when you angrily reject this invitation.
Appearances are all there is with narcissists -- and their self-hatred knows no bounds.
Do not write a letter to your mother either, this will be used against you by her. I would instead suggest you write an open letter to your mother then destroy it afterwards.