It is very difficult to know who was in the right or wrong without being there. Having a six year daugter of my own, I do however have to pose the question, what on earth was going through your mind taking her into the fever zone? Was that just a magic cluster fudge?
So it is right to verbally abuse someone after 90 mins? Do you really need to think about that?
Grandma is over on holiday, we all went to the match together. All three of my kids have been in the zone before I have a season ticket. There was another girl of similar age sitting right behind us, plus there were quite a few other youngsters. I don't/didn't see it as a problem - each to their own.