I suppose this must be a common problem, and potentially a tricky diplomatic one. Vicky seemed to believe that the mother's parents always (and rightly) had first dibsies, but is that a widespread convention? There was no such competition in the case of my own grandparents: they were Nana and Grandpa on my mother's side, but my paternal grandmother died before I was born, and my grandfather on that side preferred to be addressed in Esperanto, as "Avo". (To be honest I thought that was his name until years after he died.) The conventions for my own children's grandparents were dull enough, but evenhanded: Grandpa/ma + First Name. It seemed to work.
Vicky is always stylish, and on this occasion was wearing a very nice Alexander McQueen cardigan. When my mother admired it, she gave it her - and I think it suits her well.
My mother turned 94 the other day.