These last 2 years have been very hard on all families. I get the impression that Grandmarosie knows she is being daft, and came on here for some advice dealing with it.
As Discodancer points out, she simply said that she left the party early. If she was feeling upset and not quite in control of her emotions, it was probably a sensible thing to do.
However, Grandmarosie, it is difficult to advise. If you know why you feel such strong emotions at normal 3 year old behaviour, that may help. I'd begin by wondering if it is the other gran you can't stand, or if being 'ignored' triggers something in you.
If you can't fathom it, I'd suggest talking to someone - a trusted friend who might have some insight - or who will just let you bitch a bit to get your perspective back! If it is really bothersome, a counsellor may help, but I think these odd times have led many of us to 'over-react'.
I don't know if you've read this far, but I hope you have found something useful