Most umps won't allow anyone to stand behind home and say anything let alone just be an observer. I'm surprised he didn't tell her to scoot.
We had an important game this year with the conference standings at stake. A player from another team (not the two playing) favored one of the two playing over the other as they would have been tied for first if the one team won. Sitting behind the fence at home plate she kept yelling "strike" very loudly on every pitch. It was obvious the umpire was displeased. Really close calls were being called "balls". The umpire may not have been influenced but I believe she was.
I am surprised this individual was allowed to continue this, based on your description.
Who was going to stop it?
I am surprised this individual was allowed to continue this, based on your description.