I've also cut my mother out. But more because she constantly hangs on every word my narcissitic sister utters and disregards me and my other two sisters. Plenty of the extended family saw my sister for what she is and warned my mum but she was so bent on being her best mate rather than her mother she refused to see it. She lives just 4 miles away but we used to live less than half a mile away and like you, only saw my kids if we made effort, yet she will, at the drop of a hat, travel 20 mile by public transport to go and see my sister's kids. It's gotten much worse in the last 5 years, since my Dad died & I believe he was the voice that was telling her she was in the wrong.
To put it into a context. About 16 years ago I found myself with no place to live after a relationship break up (ex cheated), my mother didn't want me back at the family home (a 4 bed house ith just her and Dad). I discovered that my sis and my ex had been talking and my sis had told my mum that she wasn't seeing her grandkids if I was allowed back home. My Dad was furious & threatened to kick her out, the only time I've seen their marriage hit rocks.
My other 2 sisters make an effort to see my kids and will often cajole my mum to come with them but I will go out of the house. I've no interest anymore. My 2 year old treats her like a stranger when she comes. But I won't stand in the way if they want a relationship with her later down the line & I'll be there to pick up the pieces when it all goes wrong.