Ugh that makes me PUKE! Your terrific Nan doing what she can to get your mum to be a human, and mum just.... grrrrr! I'm so sorry. Does your Nan have a mobile, or is there any other way that you can contact her?
The other day my mum called, I was surprised and happy (and worried) as I answered the phone, but there were no words, just the sound of something being broken or ripped. I sms'd with 'was that the sound of tiles being chipped off the walls?', assuming that she'd called accidentally, during their renos. It's since occurred to me that it was the sound of my stuff being ripped up and broken, and afterwards she was too ashamed to admit that she's that vindictive and crazy.
My mum is going insane, it might be true of yours too. There's nothing we can do about it; it's the product of the years of mind games that they even signed up for themselves. The thing they want from us is impossible to deliver. They're going to burn themselves up.
Just love your three babes! They've taken enough of your happiness.