Why all the fuss about calling a badly behaved child horrid? Honestly I only have to go to the local town, in a reasonable area and I hear harassed Mothers saying things to their children in a harsh way.
This Gran was tired, and was dealing with a very rude child late evening, who was being obnoxious. Its human nature.
I have said things like that to my Grandsons, and like I said upthread, they love me, they could not care less about what I said to them at 5 years of age. It's forgot about. The child was not hit, abused or shaken.
Honestly, some of you are so judgemental, and I don't believe that you have always got it right.
The Mothers behavior was dreadful and where her daughter is concerned the apple never fell far from the tree.
I hope Gran does not apologise and the daughter finds someone else to look after her daughter. Good luck with that, if people know what she's like.