I've been following this thread for a while, and have debated whether or not to post, as I'm not a Gran, but a DIL with a manipulative, nasty MIL. Apologies - this is likely to be long!
I believe that there are 'toxic' people in all walks of life, and it's sheer bad luck to encounter then as a Mum, MIL, DIL - or whoever. My heart goes out to those of you experiencing clear pain on a daily basis; I can't begin to understand how much it hurts not to see those you crave a close relationship with.
I'm not estranged from my MIL, although we've come close. Being in her life (and allowing her to have contact with my children) is a constant battle, and leaves me feeling sick and shaky every time I see her. I do so for my husband, as I don't believe it's right for me (in my particular circumstances) to draw lines in how their relationship will be.
My MIL would tell you that I am difficult, and cold, and stuck up (she's said these things to me frequently). I am just anxious around her, and while she is wonderful at acting caring and loving in front of others, when alone she has acted despicably and denied it, laughing while I questioned my own mind.
There's a very long history, which I won't bore you all with, but highlights include mocking me about my childhood abuser, and telling me that she had shown this person photos of my children, purposefully making my child cry and smirking at me, then denying it when my husband walked in, and undermining me at every opportunity while smiling and laughing at my distress.
On the outside, she appears caring and generous, but even my husband agrees that she has an evil streak. As much as I would love not to see her, my husband would take the children without me (as he hadn't seen her grabbing their wrists, making them cry etc) and I have to be there to protect them.
The decision not to go NC is partly as I am strong enough to monitor her relationship with my children, although if her behaviour worsens, who knows. I have to protect them from her nasty streak.
I don't know how things will end; she's in her 70s, and I'd love for us to get along, and enjoy Christmases and birthdays together for my DH and children's sake. I just don't know if her behaviour will allow this, which is sad, as I believe that she wants this too, just with me out of the picture.